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<h3><a href="../contents.html">Table of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">Initialization, Finalization, and Threads</a><ul>
<li><a class="reference internal" href="#before-python-initialization">Before Python Initialization</a></li>
<li><a class="reference internal" href="#global-configuration-variables">Global configuration variables</a></li>
<li><a class="reference internal" href="#initializing-and-finalizing-the-interpreter">Initializing and finalizing the interpreter</a></li>
<li><a class="reference internal" href="#process-wide-parameters">Process-wide parameters</a></li>
<li><a class="reference internal" href="#thread-state-and-the-global-interpreter-lock">Thread State and the Global Interpreter Lock</a><ul>
<li><a class="reference internal" href="#detaching-the-thread-state-from-extension-code">Detaching the thread state from extension code</a></li>
<li><a class="reference internal" href="#non-python-created-threads">Non-Python created threads</a></li>
<li><a class="reference internal" href="#supporting-subinterpreters-in-non-python-threads">Supporting subinterpreters in non-Python threads</a></li>
<li><a class="reference internal" href="#cautions-about-fork">Cautions about fork()</a></li>
<li><a class="reference internal" href="#cautions-regarding-runtime-finalization">Cautions regarding runtime finalization</a></li>
<li><a class="reference internal" href="#high-level-api">High-level API</a></li>
<li><a class="reference internal" href="#low-level-api">Low-level API</a></li>
</ul>
</li>
<li><a class="reference internal" href="#sub-interpreter-support">Sub-interpreter support</a><ul>
<li><a class="reference internal" href="#a-per-interpreter-gil">A Per-Interpreter GIL</a></li>
<li><a class="reference internal" href="#bugs-and-caveats">Bugs and caveats</a></li>
</ul>
</li>
<li><a class="reference internal" href="#asynchronous-notifications">Asynchronous Notifications</a></li>
<li><a class="reference internal" href="#profiling-and-tracing">Profiling and Tracing</a></li>
<li><a class="reference internal" href="#reference-tracing">Reference tracing</a></li>
<li><a class="reference internal" href="#advanced-debugger-support">Advanced Debugger Support</a></li>
<li><a class="reference internal" href="#thread-local-storage-support">Thread Local Storage Support</a><ul>
<li><a class="reference internal" href="#thread-specific-storage-tss-api">Thread Specific Storage (TSS) API</a><ul>
<li><a class="reference internal" href="#dynamic-allocation">Dynamic Allocation</a></li>
<li><a class="reference internal" href="#methods">Methods</a></li>
</ul>
</li>
<li><a class="reference internal" href="#thread-local-storage-tls-api">Thread Local Storage (TLS) API</a></li>
</ul>
</li>
<li><a class="reference internal" href="#synchronization-primitives">Synchronization Primitives</a><ul>
<li><a class="reference internal" href="#python-critical-section-api">Python Critical Section API</a></li>
</ul>
</li>
</ul>
</li>
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<p class="topless"><a href="typehints.html"
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<section id="initialization-finalization-and-threads">
<span id="initialization"></span><h1>Initialization, Finalization, and Threads<a class="headerlink" href="#initialization-finalization-and-threads" title="Link to this heading">¶</a></h1>
<p>See <a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python Initialization Configuration</span></a> for details
on how to configure the interpreter prior to initialization.</p>
<section id="before-python-initialization">
<span id="pre-init-safe"></span><h2>Before Python Initialization<a class="headerlink" href="#before-python-initialization" title="Link to this heading">¶</a></h2>
<p>In an application embedding Python, the <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a> function must
be called before using any other Python/C API functions; with the exception of
a few functions and the <a class="reference internal" href="#global-conf-vars"><span class="std std-ref">global configuration variables</span></a>.</p>
<p>The following functions can be safely called before Python is initialized:</p>
<ul class="simple">
<li><p>Functions that initialize the interpreter:</p>
<ul>
<li><p><a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.Py_InitializeEx" title="Py_InitializeEx"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_InitializeEx()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.Py_InitializeFromConfig" title="Py_InitializeFromConfig"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_InitializeFromConfig()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.Py_BytesMain" title="Py_BytesMain"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_BytesMain()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.Py_Main" title="Py_Main"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Main()</span></code></a></p></li>
<li><p>the runtime pre-initialization functions covered in <a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python Initialization Configuration</span></a></p></li>
</ul>
</li>
<li><p>Configuration functions:</p>
<ul>
<li><p><a class="reference internal" href="import.html#c.PyImport_AppendInittab" title="PyImport_AppendInittab"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyImport_AppendInittab()</span></code></a></p></li>
<li><p><a class="reference internal" href="import.html#c.PyImport_ExtendInittab" title="PyImport_ExtendInittab"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyImport_ExtendInittab()</span></code></a></p></li>
<li><p><code class="xref c c-func docutils literal notranslate"><span class="pre">PyInitFrozenExtensions()</span></code></p></li>
<li><p><a class="reference internal" href="memory.html#c.PyMem_SetAllocator" title="PyMem_SetAllocator"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyMem_SetAllocator()</span></code></a></p></li>
<li><p><a class="reference internal" href="memory.html#c.PyMem_SetupDebugHooks" title="PyMem_SetupDebugHooks"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyMem_SetupDebugHooks()</span></code></a></p></li>
<li><p><a class="reference internal" href="memory.html#c.PyObject_SetArenaAllocator" title="PyObject_SetArenaAllocator"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyObject_SetArenaAllocator()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.Py_SetProgramName" title="Py_SetProgramName"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_SetProgramName()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.Py_SetPythonHome" title="Py_SetPythonHome"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_SetPythonHome()</span></code></a></p></li>
<li><p><a class="reference internal" href="sys.html#c.PySys_ResetWarnOptions" title="PySys_ResetWarnOptions"><code class="xref c c-func docutils literal notranslate"><span class="pre">PySys_ResetWarnOptions()</span></code></a></p></li>
<li><p>the configuration functions covered in <a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python Initialization Configuration</span></a></p></li>
</ul>
</li>
<li><p>Informative functions:</p>
<ul>
<li><p><a class="reference internal" href="#c.Py_IsInitialized" title="Py_IsInitialized"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_IsInitialized()</span></code></a></p></li>
<li><p><a class="reference internal" href="memory.html#c.PyMem_GetAllocator" title="PyMem_GetAllocator"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyMem_GetAllocator()</span></code></a></p></li>
<li><p><a class="reference internal" href="memory.html#c.PyObject_GetArenaAllocator" title="PyObject_GetArenaAllocator"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyObject_GetArenaAllocator()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.Py_GetBuildInfo" title="Py_GetBuildInfo"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_GetBuildInfo()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.Py_GetCompiler" title="Py_GetCompiler"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_GetCompiler()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.Py_GetCopyright" title="Py_GetCopyright"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_GetCopyright()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.Py_GetPlatform" title="Py_GetPlatform"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_GetPlatform()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.Py_GetVersion" title="Py_GetVersion"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_GetVersion()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.Py_IsInitialized" title="Py_IsInitialized"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_IsInitialized()</span></code></a></p></li>
</ul>
</li>
<li><p>Utilities:</p>
<ul>
<li><p><a class="reference internal" href="sys.html#c.Py_DecodeLocale" title="Py_DecodeLocale"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_DecodeLocale()</span></code></a></p></li>
<li><p>the status reporting and utility functions covered in <a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python Initialization Configuration</span></a></p></li>
</ul>
</li>
<li><p>Memory allocators:</p>
<ul>
<li><p><a class="reference internal" href="memory.html#c.PyMem_RawMalloc" title="PyMem_RawMalloc"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyMem_RawMalloc()</span></code></a></p></li>
<li><p><a class="reference internal" href="memory.html#c.PyMem_RawRealloc" title="PyMem_RawRealloc"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyMem_RawRealloc()</span></code></a></p></li>
<li><p><a class="reference internal" href="memory.html#c.PyMem_RawCalloc" title="PyMem_RawCalloc"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyMem_RawCalloc()</span></code></a></p></li>
<li><p><a class="reference internal" href="memory.html#c.PyMem_RawFree" title="PyMem_RawFree"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyMem_RawFree()</span></code></a></p></li>
</ul>
</li>
<li><p>Synchronization:</p>
<ul>
<li><p><a class="reference internal" href="#c.PyMutex_Lock" title="PyMutex_Lock"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyMutex_Lock()</span></code></a></p></li>
<li><p><a class="reference internal" href="#c.PyMutex_Unlock" title="PyMutex_Unlock"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyMutex_Unlock()</span></code></a></p></li>
</ul>
</li>
</ul>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>Despite their apparent similarity to some of the functions listed above,
the following functions <strong>should not be called</strong> before the interpreter has
been initialized: <a class="reference internal" href="sys.html#c.Py_EncodeLocale" title="Py_EncodeLocale"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_EncodeLocale()</span></code></a>, <a class="reference internal" href="#c.Py_GetPath" title="Py_GetPath"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_GetPath()</span></code></a>,
<a class="reference internal" href="#c.Py_GetPrefix" title="Py_GetPrefix"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_GetPrefix()</span></code></a>, <a class="reference internal" href="#c.Py_GetExecPrefix" title="Py_GetExecPrefix"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_GetExecPrefix()</span></code></a>,
<a class="reference internal" href="#c.Py_GetProgramFullPath" title="Py_GetProgramFullPath"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_GetProgramFullPath()</span></code></a>, <a class="reference internal" href="#c.Py_GetPythonHome" title="Py_GetPythonHome"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_GetPythonHome()</span></code></a>,
<a class="reference internal" href="#c.Py_GetProgramName" title="Py_GetProgramName"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_GetProgramName()</span></code></a>, <a class="reference internal" href="#c.PyEval_InitThreads" title="PyEval_InitThreads"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyEval_InitThreads()</span></code></a>, and
<a class="reference internal" href="#c.Py_RunMain" title="Py_RunMain"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_RunMain()</span></code></a>.</p>
</div>
</section>
<section id="global-configuration-variables">
<span id="global-conf-vars"></span><h2>Global configuration variables<a class="headerlink" href="#global-configuration-variables" title="Link to this heading">¶</a></h2>
<p>Python has variables for the global configuration to control different features
and options. By default, these flags are controlled by <a class="reference internal" href="../using/cmdline.html#using-on-interface-options"><span class="std std-ref">command line
options</span></a>.</p>
<p>When a flag is set by an option, the value of the flag is the number of times
that the option was set. For example, <code class="docutils literal notranslate"><span class="pre">-b</span></code> sets <a class="reference internal" href="#c.Py_BytesWarningFlag" title="Py_BytesWarningFlag"><code class="xref c c-data docutils literal notranslate"><span class="pre">Py_BytesWarningFlag</span></code></a>
to 1 and <code class="docutils literal notranslate"><span class="pre">-bb</span></code> sets <a class="reference internal" href="#c.Py_BytesWarningFlag" title="Py_BytesWarningFlag"><code class="xref c c-data docutils literal notranslate"><span class="pre">Py_BytesWarningFlag</span></code></a> to 2.</p>
<dl class="c var">
<dt class="sig sig-object c" id="c.Py_BytesWarningFlag">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_BytesWarningFlag</span></span></span><a class="headerlink" href="#c.Py_BytesWarningFlag" title="Link to this definition">¶</a><br /></dt>
<dd><p>This API is kept for backward compatibility: setting
<a class="reference internal" href="init_config.html#c.PyConfig.bytes_warning" title="PyConfig.bytes_warning"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.bytes_warning</span></code></a> should be used instead, see <a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python
Initialization Configuration</span></a>.</p>
<p>Issue a warning when comparing <a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> or <a class="reference internal" href="../library/stdtypes.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytearray</span></code></a> with
<a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a> or <a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> with <a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate"><span class="pre">int</span></code></a>. Issue an error if greater
or equal to <code class="docutils literal notranslate"><span class="pre">2</span></code>.</p>
<p>Set by the <a class="reference internal" href="../using/cmdline.html#cmdoption-b"><code class="xref std std-option docutils literal notranslate"><span class="pre">-b</span></code></a> option.</p>
<div class="deprecated-removed">
<p><span class="versionmodified deprecated">Deprecated since version 3.12, will be removed in version 3.15.</span></p>
</div>
</dd></dl>
<dl class="c var">
<dt class="sig sig-object c" id="c.Py_DebugFlag">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_DebugFlag</span></span></span><a class="headerlink" href="#c.Py_DebugFlag" title="Link to this definition">¶</a><br /></dt>
<dd><p>This API is kept for backward compatibility: setting
<a class="reference internal" href="init_config.html#c.PyConfig.parser_debug" title="PyConfig.parser_debug"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.parser_debug</span></code></a> should be used instead, see <a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python
Initialization Configuration</span></a>.</p>
<p>Turn on parser debugging output (for expert only, depending on compilation
options).</p>
<p>Set by the <a class="reference internal" href="../using/cmdline.html#cmdoption-d"><code class="xref std std-option docutils literal notranslate"><span class="pre">-d</span></code></a> option and the <span class="target" id="index-0"></span><a class="reference internal" href="../using/cmdline.html#envvar-PYTHONDEBUG"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONDEBUG</span></code></a> environment
variable.</p>
<div class="deprecated-removed">
<p><span class="versionmodified deprecated">Deprecated since version 3.12, will be removed in version 3.15.</span></p>
</div>
</dd></dl>
<dl class="c var">
<dt class="sig sig-object c" id="c.Py_DontWriteBytecodeFlag">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_DontWriteBytecodeFlag</span></span></span><a class="headerlink" href="#c.Py_DontWriteBytecodeFlag" title="Link to this definition">¶</a><br /></dt>
<dd><p>This API is kept for backward compatibility: setting
<a class="reference internal" href="init_config.html#c.PyConfig.write_bytecode" title="PyConfig.write_bytecode"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.write_bytecode</span></code></a> should be used instead, see <a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python
Initialization Configuration</span></a>.</p>
<p>If set to non-zero, Python won’t try to write <code class="docutils literal notranslate"><span class="pre">.pyc</span></code> files on the
import of source modules.</p>
<p>Set by the <a class="reference internal" href="../using/cmdline.html#cmdoption-B"><code class="xref std std-option docutils literal notranslate"><span class="pre">-B</span></code></a> option and the <span class="target" id="index-1"></span><a class="reference internal" href="../using/cmdline.html#envvar-PYTHONDONTWRITEBYTECODE"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONDONTWRITEBYTECODE</span></code></a>
environment variable.</p>
<div class="deprecated-removed">
<p><span class="versionmodified deprecated">Deprecated since version 3.12, will be removed in version 3.15.</span></p>
</div>
</dd></dl>
<dl class="c var">
<dt class="sig sig-object c" id="c.Py_FrozenFlag">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_FrozenFlag</span></span></span><a class="headerlink" href="#c.Py_FrozenFlag" title="Link to this definition">¶</a><br /></dt>
<dd><p>This API is kept for backward compatibility: setting
<a class="reference internal" href="init_config.html#c.PyConfig.pathconfig_warnings" title="PyConfig.pathconfig_warnings"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.pathconfig_warnings</span></code></a> should be used instead, see
<a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python Initialization Configuration</span></a>.</p>
<p>Suppress error messages when calculating the module search path in
<a class="reference internal" href="#c.Py_GetPath" title="Py_GetPath"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_GetPath()</span></code></a>.</p>
<p>Private flag used by <code class="docutils literal notranslate"><span class="pre">_freeze_module</span></code> and <code class="docutils literal notranslate"><span class="pre">frozenmain</span></code> programs.</p>
<div class="deprecated-removed">
<p><span class="versionmodified deprecated">Deprecated since version 3.12, will be removed in version 3.15.</span></p>
</div>
</dd></dl>
<dl class="c var">
<dt class="sig sig-object c" id="c.Py_HashRandomizationFlag">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_HashRandomizationFlag</span></span></span><a class="headerlink" href="#c.Py_HashRandomizationFlag" title="Link to this definition">¶</a><br /></dt>
<dd><p>This API is kept for backward compatibility: setting
<a class="reference internal" href="init_config.html#c.PyConfig.hash_seed" title="PyConfig.hash_seed"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.hash_seed</span></code></a> and <a class="reference internal" href="init_config.html#c.PyConfig.use_hash_seed" title="PyConfig.use_hash_seed"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.use_hash_seed</span></code></a> should
be used instead, see <a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python Initialization Configuration</span></a>.</p>
<p>Set to <code class="docutils literal notranslate"><span class="pre">1</span></code> if the <span class="target" id="index-2"></span><a class="reference internal" href="../using/cmdline.html#envvar-PYTHONHASHSEED"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONHASHSEED</span></code></a> environment variable is set to
a non-empty string.</p>
<p>If the flag is non-zero, read the <span class="target" id="index-3"></span><a class="reference internal" href="../using/cmdline.html#envvar-PYTHONHASHSEED"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONHASHSEED</span></code></a> environment
variable to initialize the secret hash seed.</p>
<div class="deprecated-removed">
<p><span class="versionmodified deprecated">Deprecated since version 3.12, will be removed in version 3.15.</span></p>
</div>
</dd></dl>
<dl class="c var">
<dt class="sig sig-object c" id="c.Py_IgnoreEnvironmentFlag">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_IgnoreEnvironmentFlag</span></span></span><a class="headerlink" href="#c.Py_IgnoreEnvironmentFlag" title="Link to this definition">¶</a><br /></dt>
<dd><p>This API is kept for backward compatibility: setting
<a class="reference internal" href="init_config.html#c.PyConfig.use_environment" title="PyConfig.use_environment"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.use_environment</span></code></a> should be used instead, see
<a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python Initialization Configuration</span></a>.</p>
<p>Ignore all <code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHON*</span></code> environment variables, e.g.
<span class="target" id="index-4"></span><a class="reference internal" href="../using/cmdline.html#envvar-PYTHONPATH"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONPATH</span></code></a> and <span class="target" id="index-5"></span><a class="reference internal" href="../using/cmdline.html#envvar-PYTHONHOME"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONHOME</span></code></a>, that might be set.</p>
<p>Set by the <a class="reference internal" href="../using/cmdline.html#cmdoption-E"><code class="xref std std-option docutils literal notranslate"><span class="pre">-E</span></code></a> and <a class="reference internal" href="../using/cmdline.html#cmdoption-I"><code class="xref std std-option docutils literal notranslate"><span class="pre">-I</span></code></a> options.</p>
<div class="deprecated-removed">
<p><span class="versionmodified deprecated">Deprecated since version 3.12, will be removed in version 3.15.</span></p>
</div>
</dd></dl>
<dl class="c var">
<dt class="sig sig-object c" id="c.Py_InspectFlag">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_InspectFlag</span></span></span><a class="headerlink" href="#c.Py_InspectFlag" title="Link to this definition">¶</a><br /></dt>
<dd><p>This API is kept for backward compatibility: setting
<a class="reference internal" href="init_config.html#c.PyConfig.inspect" title="PyConfig.inspect"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.inspect</span></code></a> should be used instead, see
<a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python Initialization Configuration</span></a>.</p>
<p>When a script is passed as first argument or the <a class="reference internal" href="../using/cmdline.html#cmdoption-c"><code class="xref std std-option docutils literal notranslate"><span class="pre">-c</span></code></a> option is used,
enter interactive mode after executing the script or the command, even when
<a class="reference internal" href="../library/sys.html#sys.stdin" title="sys.stdin"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.stdin</span></code></a> does not appear to be a terminal.</p>
<p>Set by the <a class="reference internal" href="../using/cmdline.html#cmdoption-i"><code class="xref std std-option docutils literal notranslate"><span class="pre">-i</span></code></a> option and the <span class="target" id="index-6"></span><a class="reference internal" href="../using/cmdline.html#envvar-PYTHONINSPECT"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONINSPECT</span></code></a> environment
variable.</p>
<div class="deprecated-removed">
<p><span class="versionmodified deprecated">Deprecated since version 3.12, will be removed in version 3.15.</span></p>
</div>
</dd></dl>
<dl class="c var">
<dt class="sig sig-object c" id="c.Py_InteractiveFlag">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_InteractiveFlag</span></span></span><a class="headerlink" href="#c.Py_InteractiveFlag" title="Link to this definition">¶</a><br /></dt>
<dd><p>This API is kept for backward compatibility: setting
<a class="reference internal" href="init_config.html#c.PyConfig.interactive" title="PyConfig.interactive"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.interactive</span></code></a> should be used instead, see
<a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python Initialization Configuration</span></a>.</p>
<p>Set by the <a class="reference internal" href="../using/cmdline.html#cmdoption-i"><code class="xref std std-option docutils literal notranslate"><span class="pre">-i</span></code></a> option.</p>
<div class="deprecated-removed">
<p><span class="versionmodified deprecated">Deprecated since version 3.12, will be removed in version 3.15.</span></p>
</div>
</dd></dl>
<dl class="c var">
<dt class="sig sig-object c" id="c.Py_IsolatedFlag">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_IsolatedFlag</span></span></span><a class="headerlink" href="#c.Py_IsolatedFlag" title="Link to this definition">¶</a><br /></dt>
<dd><p>This API is kept for backward compatibility: setting
<a class="reference internal" href="init_config.html#c.PyConfig.isolated" title="PyConfig.isolated"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.isolated</span></code></a> should be used instead, see
<a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python Initialization Configuration</span></a>.</p>
<p>Run Python in isolated mode. In isolated mode <a class="reference internal" href="../library/sys.html#sys.path" title="sys.path"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path</span></code></a> contains
neither the script’s directory nor the user’s site-packages directory.</p>
<p>Set by the <a class="reference internal" href="../using/cmdline.html#cmdoption-I"><code class="xref std std-option docutils literal notranslate"><span class="pre">-I</span></code></a> option.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.4.</span></p>
</div>
<div class="deprecated-removed">
<p><span class="versionmodified deprecated">Deprecated since version 3.12, will be removed in version 3.15.</span></p>
</div>
</dd></dl>
<dl class="c var">
<dt class="sig sig-object c" id="c.Py_LegacyWindowsFSEncodingFlag">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_LegacyWindowsFSEncodingFlag</span></span></span><a class="headerlink" href="#c.Py_LegacyWindowsFSEncodingFlag" title="Link to this definition">¶</a><br /></dt>
<dd><p>This API is kept for backward compatibility: setting
<a class="reference internal" href="init_config.html#c.PyPreConfig.legacy_windows_fs_encoding" title="PyPreConfig.legacy_windows_fs_encoding"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyPreConfig.legacy_windows_fs_encoding</span></code></a> should be used instead, see
<a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python Initialization Configuration</span></a>.</p>
<p>If the flag is non-zero, use the <code class="docutils literal notranslate"><span class="pre">mbcs</span></code> encoding with <code class="docutils literal notranslate"><span class="pre">replace</span></code> error
handler, instead of the UTF-8 encoding with <code class="docutils literal notranslate"><span class="pre">surrogatepass</span></code> error handler,
for the <a class="reference internal" href="../glossary.html#term-filesystem-encoding-and-error-handler"><span class="xref std std-term">filesystem encoding and error handler</span></a>.</p>
<p>Set to <code class="docutils literal notranslate"><span class="pre">1</span></code> if the <span class="target" id="index-7"></span><a class="reference internal" href="../using/cmdline.html#envvar-PYTHONLEGACYWINDOWSFSENCODING"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONLEGACYWINDOWSFSENCODING</span></code></a> environment
variable is set to a non-empty string.</p>
<p>See <span class="target" id="index-8"></span><a class="pep reference external" href="https://peps.python.org/pep-0529/"><strong>PEP 529</strong></a> for more details.</p>
<div class="availability docutils container">
<p><a class="reference internal" href="../library/intro.html#availability"><span class="std std-ref">Availability</span></a>: Windows.</p>
</div>
<div class="deprecated-removed">
<p><span class="versionmodified deprecated">Deprecated since version 3.12, will be removed in version 3.15.</span></p>
</div>
</dd></dl>
<dl class="c var">
<dt class="sig sig-object c" id="c.Py_LegacyWindowsStdioFlag">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_LegacyWindowsStdioFlag</span></span></span><a class="headerlink" href="#c.Py_LegacyWindowsStdioFlag" title="Link to this definition">¶</a><br /></dt>
<dd><p>This API is kept for backward compatibility: setting
<a class="reference internal" href="init_config.html#c.PyConfig.legacy_windows_stdio" title="PyConfig.legacy_windows_stdio"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.legacy_windows_stdio</span></code></a> should be used instead, see
<a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python Initialization Configuration</span></a>.</p>
<p>If the flag is non-zero, use <a class="reference internal" href="../library/io.html#io.FileIO" title="io.FileIO"><code class="xref py py-class docutils literal notranslate"><span class="pre">io.FileIO</span></code></a> instead of
<code class="xref py py-class docutils literal notranslate"><span class="pre">io._WindowsConsoleIO</span></code> for <a class="reference internal" href="../library/sys.html#module-sys" title="sys: Access system-specific parameters and functions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">sys</span></code></a> standard streams.</p>
<p>Set to <code class="docutils literal notranslate"><span class="pre">1</span></code> if the <span class="target" id="index-9"></span><a class="reference internal" href="../using/cmdline.html#envvar-PYTHONLEGACYWINDOWSSTDIO"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONLEGACYWINDOWSSTDIO</span></code></a> environment
variable is set to a non-empty string.</p>
<p>See <span class="target" id="index-10"></span><a class="pep reference external" href="https://peps.python.org/pep-0528/"><strong>PEP 528</strong></a> for more details.</p>
<div class="availability docutils container">
<p><a class="reference internal" href="../library/intro.html#availability"><span class="std std-ref">Availability</span></a>: Windows.</p>
</div>
<div class="deprecated-removed">
<p><span class="versionmodified deprecated">Deprecated since version 3.12, will be removed in version 3.15.</span></p>
</div>
</dd></dl>
<dl class="c var">
<dt class="sig sig-object c" id="c.Py_NoSiteFlag">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_NoSiteFlag</span></span></span><a class="headerlink" href="#c.Py_NoSiteFlag" title="Link to this definition">¶</a><br /></dt>
<dd><p>This API is kept for backward compatibility: setting
<a class="reference internal" href="init_config.html#c.PyConfig.site_import" title="PyConfig.site_import"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.site_import</span></code></a> should be used instead, see
<a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python Initialization Configuration</span></a>.</p>
<p>Disable the import of the module <a class="reference internal" href="../library/site.html#module-site" title="site: Module responsible for site-specific configuration."><code class="xref py py-mod docutils literal notranslate"><span class="pre">site</span></code></a> and the site-dependent
manipulations of <a class="reference internal" href="../library/sys.html#sys.path" title="sys.path"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path</span></code></a> that it entails. Also disable these
manipulations if <a class="reference internal" href="../library/site.html#module-site" title="site: Module responsible for site-specific configuration."><code class="xref py py-mod docutils literal notranslate"><span class="pre">site</span></code></a> is explicitly imported later (call
<a class="reference internal" href="../library/site.html#site.main" title="site.main"><code class="xref py py-func docutils literal notranslate"><span class="pre">site.main()</span></code></a> if you want them to be triggered).</p>
<p>Set by the <a class="reference internal" href="../using/cmdline.html#cmdoption-S"><code class="xref std std-option docutils literal notranslate"><span class="pre">-S</span></code></a> option.</p>
<div class="deprecated-removed">
<p><span class="versionmodified deprecated">Deprecated since version 3.12, will be removed in version 3.15.</span></p>
</div>
</dd></dl>
<dl class="c var">
<dt class="sig sig-object c" id="c.Py_NoUserSiteDirectory">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_NoUserSiteDirectory</span></span></span><a class="headerlink" href="#c.Py_NoUserSiteDirectory" title="Link to this definition">¶</a><br /></dt>
<dd><p>This API is kept for backward compatibility: setting
<a class="reference internal" href="init_config.html#c.PyConfig.user_site_directory" title="PyConfig.user_site_directory"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.user_site_directory</span></code></a> should be used instead, see
<a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python Initialization Configuration</span></a>.</p>
<p>Don’t add the <a class="reference internal" href="../library/site.html#site.USER_SITE" title="site.USER_SITE"><code class="xref py py-data docutils literal notranslate"><span class="pre">user</span> <span class="pre">site-packages</span> <span class="pre">directory</span></code></a> to
<a class="reference internal" href="../library/sys.html#sys.path" title="sys.path"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path</span></code></a>.</p>
<p>Set by the <a class="reference internal" href="../using/cmdline.html#cmdoption-s"><code class="xref std std-option docutils literal notranslate"><span class="pre">-s</span></code></a> and <a class="reference internal" href="../using/cmdline.html#cmdoption-I"><code class="xref std std-option docutils literal notranslate"><span class="pre">-I</span></code></a> options, and the
<span class="target" id="index-11"></span><a class="reference internal" href="../using/cmdline.html#envvar-PYTHONNOUSERSITE"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONNOUSERSITE</span></code></a> environment variable.</p>
<div class="deprecated-removed">
<p><span class="versionmodified deprecated">Deprecated since version 3.12, will be removed in version 3.15.</span></p>
</div>
</dd></dl>
<dl class="c var">
<dt class="sig sig-object c" id="c.Py_OptimizeFlag">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_OptimizeFlag</span></span></span><a class="headerlink" href="#c.Py_OptimizeFlag" title="Link to this definition">¶</a><br /></dt>
<dd><p>This API is kept for backward compatibility: setting
<a class="reference internal" href="init_config.html#c.PyConfig.optimization_level" title="PyConfig.optimization_level"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.optimization_level</span></code></a> should be used instead, see
<a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python Initialization Configuration</span></a>.</p>
<p>Set by the <a class="reference internal" href="../using/cmdline.html#cmdoption-O"><code class="xref std std-option docutils literal notranslate"><span class="pre">-O</span></code></a> option and the <span class="target" id="index-12"></span><a class="reference internal" href="../using/cmdline.html#envvar-PYTHONOPTIMIZE"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONOPTIMIZE</span></code></a> environment
variable.</p>
<div class="deprecated-removed">
<p><span class="versionmodified deprecated">Deprecated since version 3.12, will be removed in version 3.15.</span></p>
</div>
</dd></dl>
<dl class="c var">
<dt class="sig sig-object c" id="c.Py_QuietFlag">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_QuietFlag</span></span></span><a class="headerlink" href="#c.Py_QuietFlag" title="Link to this definition">¶</a><br /></dt>
<dd><p>This API is kept for backward compatibility: setting
<a class="reference internal" href="init_config.html#c.PyConfig.quiet" title="PyConfig.quiet"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.quiet</span></code></a> should be used instead, see <a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python
Initialization Configuration</span></a>.</p>
<p>Don’t display the copyright and version messages even in interactive mode.</p>
<p>Set by the <a class="reference internal" href="../using/cmdline.html#cmdoption-q"><code class="xref std std-option docutils literal notranslate"><span class="pre">-q</span></code></a> option.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.2.</span></p>
</div>
<div class="deprecated-removed">
<p><span class="versionmodified deprecated">Deprecated since version 3.12, will be removed in version 3.15.</span></p>
</div>
</dd></dl>
<dl class="c var">
<dt class="sig sig-object c" id="c.Py_UnbufferedStdioFlag">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_UnbufferedStdioFlag</span></span></span><a class="headerlink" href="#c.Py_UnbufferedStdioFlag" title="Link to this definition">¶</a><br /></dt>
<dd><p>This API is kept for backward compatibility: setting
<a class="reference internal" href="init_config.html#c.PyConfig.buffered_stdio" title="PyConfig.buffered_stdio"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.buffered_stdio</span></code></a> should be used instead, see <a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python
Initialization Configuration</span></a>.</p>
<p>Force the stdout and stderr streams to be unbuffered.</p>
<p>Set by the <a class="reference internal" href="../using/cmdline.html#cmdoption-u"><code class="xref std std-option docutils literal notranslate"><span class="pre">-u</span></code></a> option and the <span class="target" id="index-13"></span><a class="reference internal" href="../using/cmdline.html#envvar-PYTHONUNBUFFERED"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONUNBUFFERED</span></code></a>
environment variable.</p>
<div class="deprecated-removed">
<p><span class="versionmodified deprecated">Deprecated since version 3.12, will be removed in version 3.15.</span></p>
</div>
</dd></dl>
<dl class="c var">
<dt class="sig sig-object c" id="c.Py_VerboseFlag">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_VerboseFlag</span></span></span><a class="headerlink" href="#c.Py_VerboseFlag" title="Link to this definition">¶</a><br /></dt>
<dd><p>This API is kept for backward compatibility: setting
<a class="reference internal" href="init_config.html#c.PyConfig.verbose" title="PyConfig.verbose"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.verbose</span></code></a> should be used instead, see <a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python
Initialization Configuration</span></a>.</p>
<p>Print a message each time a module is initialized, showing the place
(filename or built-in module) from which it is loaded. If greater or equal
to <code class="docutils literal notranslate"><span class="pre">2</span></code>, print a message for each file that is checked for when
searching for a module. Also provides information on module cleanup at exit.</p>
<p>Set by the <a class="reference internal" href="../using/cmdline.html#cmdoption-v"><code class="xref std std-option docutils literal notranslate"><span class="pre">-v</span></code></a> option and the <span class="target" id="index-14"></span><a class="reference internal" href="../using/cmdline.html#envvar-PYTHONVERBOSE"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONVERBOSE</span></code></a> environment
variable.</p>
<div class="deprecated-removed">
<p><span class="versionmodified deprecated">Deprecated since version 3.12, will be removed in version 3.15.</span></p>
</div>
</dd></dl>
</section>
<section id="initializing-and-finalizing-the-interpreter">
<h2>Initializing and finalizing the interpreter<a class="headerlink" href="#initializing-and-finalizing-the-interpreter" title="Link to this heading">¶</a></h2>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_Initialize">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_Initialize</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_Initialize" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p id="index-15">Initialize the Python interpreter. In an application embedding Python,
this should be called before using any other Python/C API functions; see
<a class="reference internal" href="#pre-init-safe"><span class="std std-ref">Before Python Initialization</span></a> for the few exceptions.</p>
<p>This initializes the table of loaded modules (<code class="docutils literal notranslate"><span class="pre">sys.modules</span></code>), and creates
the fundamental modules <a class="reference internal" href="../library/builtins.html#module-builtins" title="builtins: The module that provides the built-in namespace."><code class="xref py py-mod docutils literal notranslate"><span class="pre">builtins</span></code></a>, <a class="reference internal" href="../library/__main__.html#module-__main__" title="__main__: The environment where top-level code is run. Covers command-line interfaces, import-time behavior, and ``__name__ == '__main__'``."><code class="xref py py-mod docutils literal notranslate"><span class="pre">__main__</span></code></a> and <a class="reference internal" href="../library/sys.html#module-sys" title="sys: Access system-specific parameters and functions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">sys</span></code></a>.
It also initializes the module search path (<code class="docutils literal notranslate"><span class="pre">sys.path</span></code>). It does not set
<code class="docutils literal notranslate"><span class="pre">sys.argv</span></code>; use the <a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python Initialization Configuration</span></a>
API for that. This is a no-op when called for a second time (without calling
<a class="reference internal" href="#c.Py_FinalizeEx" title="Py_FinalizeEx"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_FinalizeEx()</span></code></a> first). There is no return value; it is a fatal
error if the initialization fails.</p>
<p>Use <a class="reference internal" href="#c.Py_InitializeFromConfig" title="Py_InitializeFromConfig"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_InitializeFromConfig()</span></code></a> to customize the
<a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python Initialization Configuration</span></a>.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>On Windows, changes the console mode from <code class="docutils literal notranslate"><span class="pre">O_TEXT</span></code> to <code class="docutils literal notranslate"><span class="pre">O_BINARY</span></code>,
which will also affect non-Python uses of the console using the C Runtime.</p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_InitializeEx">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_InitializeEx</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">initsigs</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_InitializeEx" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>This function works like <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a> if <em>initsigs</em> is <code class="docutils literal notranslate"><span class="pre">1</span></code>. If
<em>initsigs</em> is <code class="docutils literal notranslate"><span class="pre">0</span></code>, it skips initialization registration of signal handlers,
which may be useful when CPython is embedded as part of a larger application.</p>
<p>Use <a class="reference internal" href="#c.Py_InitializeFromConfig" title="Py_InitializeFromConfig"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_InitializeFromConfig()</span></code></a> to customize the
<a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python Initialization Configuration</span></a>.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_InitializeFromConfig">
<a class="reference internal" href="init_config.html#c.PyStatus" title="PyStatus"><span class="n"><span class="pre">PyStatus</span></span></a><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_InitializeFromConfig</span></span></span><span class="sig-paren">(</span><span class="k"><span class="pre">const</span></span><span class="w"> </span><a class="reference internal" href="init_config.html#c.PyConfig" title="PyConfig"><span class="n"><span class="pre">PyConfig</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">config</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_InitializeFromConfig" title="Link to this definition">¶</a><br /></dt>
<dd><p>Initialize Python from <em>config</em> configuration, as described in
<a class="reference internal" href="init_config.html#init-from-config"><span class="std std-ref">Initialization with PyConfig</span></a>.</p>
<p>See the <a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python Initialization Configuration</span></a> section for details on pre-initializing the
interpreter, populating the runtime configuration structure, and querying
the returned status structure.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_IsInitialized">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_IsInitialized</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_IsInitialized" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Return true (nonzero) when the Python interpreter has been initialized, false
(zero) if not. After <a class="reference internal" href="#c.Py_FinalizeEx" title="Py_FinalizeEx"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_FinalizeEx()</span></code></a> is called, this returns false until
<a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a> is called again.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_IsFinalizing">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_IsFinalizing</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_IsFinalizing" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.13.</em><p>Return true (non-zero) if the main Python interpreter is
<a class="reference internal" href="../glossary.html#term-interpreter-shutdown"><span class="xref std std-term">shutting down</span></a>. Return false (zero) otherwise.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.13.</span></p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_FinalizeEx">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_FinalizeEx</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_FinalizeEx" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.6.</em><p>Undo all initializations made by <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a> and subsequent use of
Python/C API functions, and destroy all sub-interpreters (see
<a class="reference internal" href="#c.Py_NewInterpreter" title="Py_NewInterpreter"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_NewInterpreter()</span></code></a> below) that were created and not yet destroyed since
the last call to <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a>. This is a no-op when called for a second
time (without calling <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a> again first).</p>
<p>Since this is the reverse of <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a>, it should be called
in the same thread with the same interpreter active. That means
the main thread and the main interpreter.
This should never be called while <a class="reference internal" href="#c.Py_RunMain" title="Py_RunMain"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_RunMain()</span></code></a> is running.</p>
<p>Normally the return value is <code class="docutils literal notranslate"><span class="pre">0</span></code>.
If there were errors during finalization (flushing buffered data),
<code class="docutils literal notranslate"><span class="pre">-1</span></code> is returned.</p>
<p>Note that Python will do a best effort at freeing all memory allocated by the Python
interpreter. Therefore, any C-Extension should make sure to correctly clean up all
of the preveiously allocated PyObjects before using them in subsequent calls to
<a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a>. Otherwise it could introduce vulnerabilities and incorrect
behavior.</p>
<p>This function is provided for a number of reasons. An embedding application
might want to restart Python without having to restart the application itself.
An application that has loaded the Python interpreter from a dynamically
loadable library (or DLL) might want to free all memory allocated by Python
before unloading the DLL. During a hunt for memory leaks in an application a
developer might want to free all memory allocated by Python before exiting from
the application.</p>
<p><strong>Bugs and caveats:</strong> The destruction of modules and objects in modules is done
in random order; this may cause destructors (<a class="reference internal" href="../reference/datamodel.html#object.__del__" title="object.__del__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__del__()</span></code></a> methods) to fail
when they depend on other objects (even functions) or modules. Dynamically
loaded extension modules loaded by Python are not unloaded. Small amounts of
memory allocated by the Python interpreter may not be freed (if you find a leak,
please report it). Memory tied up in circular references between objects is not
freed. Interned strings will all be deallocated regardless of their reference count.
Some memory allocated by extension modules may not be freed. Some extensions may not
work properly if their initialization routine is called more than once; this can
happen if an application calls <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a> and <a class="reference internal" href="#c.Py_FinalizeEx" title="Py_FinalizeEx"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_FinalizeEx()</span></code></a>
more than once. <a class="reference internal" href="#c.Py_FinalizeEx" title="Py_FinalizeEx"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_FinalizeEx()</span></code></a> must not be called recursively from
within itself. Therefore, it must not be called by any code that may be run
as part of the interpreter shutdown process, such as <a class="reference internal" href="../library/atexit.html#module-atexit" title="atexit: Register and execute cleanup functions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">atexit</span></code></a>
handlers, object finalizers, or any code that may be run while flushing the
stdout and stderr files.</p>
<p class="audit-hook">Raises an <a class="reference internal" href="../library/sys.html#auditing"><span class="std std-ref">auditing event</span></a> <code class="docutils literal notranslate"><span class="pre">cpython._PySys_ClearAuditHooks</span></code> with no arguments.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.6.</span></p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_Finalize">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_Finalize</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_Finalize" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>This is a backwards-compatible version of <a class="reference internal" href="#c.Py_FinalizeEx" title="Py_FinalizeEx"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_FinalizeEx()</span></code></a> that
disregards the return value.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_BytesMain">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_BytesMain</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">argc</span></span>, <span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">argv</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_BytesMain" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.8.</em><p>Similar to <a class="reference internal" href="#c.Py_Main" title="Py_Main"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Main()</span></code></a> but <em>argv</em> is an array of bytes strings,
allowing the calling application to delegate the text decoding step to
the CPython runtime.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.8.</span></p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_Main">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_Main</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">argc</span></span>, <span class="n"><span class="pre">wchar_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">argv</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_Main" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>The main program for the standard interpreter, encapsulating a full
initialization/finalization cycle, as well as additional
behaviour to implement reading configurations settings from the environment
and command line, and then executing <code class="docutils literal notranslate"><span class="pre">__main__</span></code> in accordance with
<a class="reference internal" href="../using/cmdline.html#using-on-cmdline"><span class="std std-ref">Command line</span></a>.</p>
<p>This is made available for programs which wish to support the full CPython
command line interface, rather than just embedding a Python runtime in a
larger application.</p>
<p>The <em>argc</em> and <em>argv</em> parameters are similar to those which are passed to a
C program’s <code class="xref c c-func docutils literal notranslate"><span class="pre">main()</span></code> function, except that the <em>argv</em> entries are first
converted to <code class="docutils literal notranslate"><span class="pre">wchar_t</span></code> using <a class="reference internal" href="sys.html#c.Py_DecodeLocale" title="Py_DecodeLocale"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_DecodeLocale()</span></code></a>. It is also
important to note that the argument list entries may be modified to point to
strings other than those passed in (however, the contents of the strings
pointed to by the argument list are not modified).</p>
<p>The return value is <code class="docutils literal notranslate"><span class="pre">2</span></code> if the argument list does not represent a valid
Python command line, and otherwise the same as <a class="reference internal" href="#c.Py_RunMain" title="Py_RunMain"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_RunMain()</span></code></a>.</p>
<p>In terms of the CPython runtime configuration APIs documented in the
<a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">runtime configuration</span></a> section (and without accounting
for error handling), <code class="docutils literal notranslate"><span class="pre">Py_Main</span></code> is approximately equivalent to:</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="n">PyConfig</span><span class="w"> </span><span class="n">config</span><span class="p">;</span>
<span class="n">PyConfig_InitPythonConfig</span><span class="p">(</span><span class="o">&</span><span class="n">config</span><span class="p">);</span>
<span class="n">PyConfig_SetArgv</span><span class="p">(</span><span class="o">&</span><span class="n">config</span><span class="p">,</span><span class="w"> </span><span class="n">argc</span><span class="p">,</span><span class="w"> </span><span class="n">argv</span><span class="p">);</span>
<span class="n">Py_InitializeFromConfig</span><span class="p">(</span><span class="o">&</span><span class="n">config</span><span class="p">);</span>
<span class="n">PyConfig_Clear</span><span class="p">(</span><span class="o">&</span><span class="n">config</span><span class="p">);</span>
<span class="n">Py_RunMain</span><span class="p">();</span>
</pre></div>
</div>
<p>In normal usage, an embedding application will call this function
<em>instead</em> of calling <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a>, <a class="reference internal" href="#c.Py_InitializeEx" title="Py_InitializeEx"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_InitializeEx()</span></code></a> or
<a class="reference internal" href="#c.Py_InitializeFromConfig" title="Py_InitializeFromConfig"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_InitializeFromConfig()</span></code></a> directly, and all settings will be applied
as described elsewhere in this documentation. If this function is instead
called <em>after</em> a preceding runtime initialization API call, then exactly
which environmental and command line configuration settings will be updated
is version dependent (as it depends on which settings correctly support
being modified after they have already been set once when the runtime was
first initialized).</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_RunMain">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_RunMain</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">void</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_RunMain" title="Link to this definition">¶</a><br /></dt>
<dd><p>Executes the main module in a fully configured CPython runtime.</p>
<p>Executes the command (<a class="reference internal" href="init_config.html#c.PyConfig.run_command" title="PyConfig.run_command"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.run_command</span></code></a>), the script
(<a class="reference internal" href="init_config.html#c.PyConfig.run_filename" title="PyConfig.run_filename"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.run_filename</span></code></a>) or the module
(<a class="reference internal" href="init_config.html#c.PyConfig.run_module" title="PyConfig.run_module"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.run_module</span></code></a>) specified on the command line or in the
configuration. If none of these values are set, runs the interactive Python
prompt (REPL) using the <code class="docutils literal notranslate"><span class="pre">__main__</span></code> module’s global namespace.</p>
<p>If <a class="reference internal" href="init_config.html#c.PyConfig.inspect" title="PyConfig.inspect"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.inspect</span></code></a> is not set (the default), the return value
will be <code class="docutils literal notranslate"><span class="pre">0</span></code> if the interpreter exits normally (that is, without raising
an exception), the exit status of an unhandled <a class="reference internal" href="../library/exceptions.html#SystemExit" title="SystemExit"><code class="xref py py-exc docutils literal notranslate"><span class="pre">SystemExit</span></code></a>, or <code class="docutils literal notranslate"><span class="pre">1</span></code>
for any other unhandled exception.</p>
<p>If <a class="reference internal" href="init_config.html#c.PyConfig.inspect" title="PyConfig.inspect"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.inspect</span></code></a> is set (such as when the <a class="reference internal" href="../using/cmdline.html#cmdoption-i"><code class="xref std std-option docutils literal notranslate"><span class="pre">-i</span></code></a> option
is used), rather than returning when the interpreter exits, execution will
instead resume in an interactive Python prompt (REPL) using the <code class="docutils literal notranslate"><span class="pre">__main__</span></code>
module’s global namespace. If the interpreter exited with an exception, it
is immediately raised in the REPL session. The function return value is
then determined by the way the <em>REPL session</em> terminates: <code class="docutils literal notranslate"><span class="pre">0</span></code>, <code class="docutils literal notranslate"><span class="pre">1</span></code>, or
the status of a <a class="reference internal" href="../library/exceptions.html#SystemExit" title="SystemExit"><code class="xref py py-exc docutils literal notranslate"><span class="pre">SystemExit</span></code></a>, as specified above.</p>
<p>This function always finalizes the Python interpreter before it returns.</p>
<p>See <a class="reference internal" href="init_config.html#init-python-config"><span class="std std-ref">Python Configuration</span></a> for an example of a
customized Python that always runs in isolated mode using
<a class="reference internal" href="#c.Py_RunMain" title="Py_RunMain"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_RunMain()</span></code></a>.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyUnstable_AtExit">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyUnstable_AtExit</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.PyInterpreterState" title="PyInterpreterState"><span class="n"><span class="pre">PyInterpreterState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">interp</span></span>, <span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="p"><span class="pre">(</span></span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">func</span></span><span class="p"><span class="pre">)</span></span><span class="p"><span class="pre">(</span></span><span class="kt"><span class="pre">void</span></span><span class="p"><span class="pre">*</span></span><span class="p"><span class="pre">)</span></span>, <span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">data</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyUnstable_AtExit" title="Link to this definition">¶</a><br /></dt>
<dd><div class="unstable-c-api warning admonition">
<em>This is <a class="reference internal" href="stable.html#unstable-c-api"><span class="std std-ref">Unstable API</span></a>. It may change without warning in minor releases.</em></div>
<p>Register an <a class="reference internal" href="../library/atexit.html#module-atexit" title="atexit: Register and execute cleanup functions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">atexit</span></code></a> callback for the target interpreter <em>interp</em>.
This is similar to <a class="reference internal" href="sys.html#c.Py_AtExit" title="Py_AtExit"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_AtExit()</span></code></a>, but takes an explicit interpreter and
data pointer for the callback.</p>
<p>There must be an <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a> for <em>interp</em>.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.13.</span></p>
</div>
</dd></dl>
</section>
<section id="process-wide-parameters">
<h2>Process-wide parameters<a class="headerlink" href="#process-wide-parameters" title="Link to this heading">¶</a></h2>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_SetProgramName">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_SetProgramName</span></span></span><span class="sig-paren">(</span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="n"><span class="pre">wchar_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">name</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_SetProgramName" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p id="index-16">This API is kept for backward compatibility: setting
<a class="reference internal" href="init_config.html#c.PyConfig.program_name" title="PyConfig.program_name"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.program_name</span></code></a> should be used instead, see <a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python
Initialization Configuration</span></a>.</p>
<p>This function should be called before <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a> is called for
the first time, if it is called at all. It tells the interpreter the value
of the <code class="docutils literal notranslate"><span class="pre">argv[0]</span></code> argument to the <code class="xref c c-func docutils literal notranslate"><span class="pre">main()</span></code> function of the program
(converted to wide characters).
This is used by <a class="reference internal" href="#c.Py_GetPath" title="Py_GetPath"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_GetPath()</span></code></a> and some other functions below to find
the Python run-time libraries relative to the interpreter executable. The
default value is <code class="docutils literal notranslate"><span class="pre">'python'</span></code>. The argument should point to a
zero-terminated wide character string in static storage whose contents will not
change for the duration of the program’s execution. No code in the Python
interpreter will change the contents of this storage.</p>
<p>Use <a class="reference internal" href="sys.html#c.Py_DecodeLocale" title="Py_DecodeLocale"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_DecodeLocale()</span></code></a> to decode a bytes string to get a
<span class="c-expr sig sig-inline c"><span class="n">wchar_t</span><span class="p">*</span></span> string.</p>
<div class="deprecated-removed">
<p><span class="versionmodified deprecated">Deprecated since version 3.11, will be removed in version 3.15.</span></p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_GetProgramName">
<span class="n"><span class="pre">wchar_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">Py_GetProgramName</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_GetProgramName" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Return the program name set with <a class="reference internal" href="init_config.html#c.PyConfig.program_name" title="PyConfig.program_name"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.program_name</span></code></a>, or the default.
The returned string points into static storage; the caller should not modify its
value.</p>
<p>This function should not be called before <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a>, otherwise
it returns <code class="docutils literal notranslate"><span class="pre">NULL</span></code>.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.10: </span>It now returns <code class="docutils literal notranslate"><span class="pre">NULL</span></code> if called before <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a>.</p>
</div>
<div class="deprecated-removed">
<p><span class="versionmodified deprecated">Deprecated since version 3.13, will be removed in version 3.15: </span>Use <a class="reference internal" href="init_config.html#c.PyConfig_Get" title="PyConfig_Get"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyConfig_Get("executable")</span></code></a>
(<a class="reference internal" href="../library/sys.html#sys.executable" title="sys.executable"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.executable</span></code></a>) instead.</p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_GetPrefix">
<span class="n"><span class="pre">wchar_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">Py_GetPrefix</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_GetPrefix" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Return the <em>prefix</em> for installed platform-independent files. This is derived
through a number of complicated rules from the program name set with
<a class="reference internal" href="init_config.html#c.PyConfig.program_name" title="PyConfig.program_name"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.program_name</span></code></a> and some environment variables; for example, if the
program name is <code class="docutils literal notranslate"><span class="pre">'/usr/local/bin/python'</span></code>, the prefix is <code class="docutils literal notranslate"><span class="pre">'/usr/local'</span></code>. The
returned string points into static storage; the caller should not modify its
value. This corresponds to the <strong class="makevar">prefix</strong> variable in the top-level
<code class="file docutils literal notranslate"><span class="pre">Makefile</span></code> and the <a class="reference internal" href="../using/configure.html#cmdoption-prefix"><code class="xref std std-option docutils literal notranslate"><span class="pre">--prefix</span></code></a> argument to the <strong class="program">configure</strong>
script at build time. The value is available to Python code as <code class="docutils literal notranslate"><span class="pre">sys.base_prefix</span></code>.
It is only useful on Unix. See also the next function.</p>
<p>This function should not be called before <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a>, otherwise
it returns <code class="docutils literal notranslate"><span class="pre">NULL</span></code>.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.10: </span>It now returns <code class="docutils literal notranslate"><span class="pre">NULL</span></code> if called before <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a>.</p>
</div>
<div class="deprecated-removed">
<p><span class="versionmodified deprecated">Deprecated since version 3.13, will be removed in version 3.15: </span>Use <a class="reference internal" href="init_config.html#c.PyConfig_Get" title="PyConfig_Get"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyConfig_Get("base_prefix")</span></code></a>
(<a class="reference internal" href="../library/sys.html#sys.base_prefix" title="sys.base_prefix"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.base_prefix</span></code></a>) instead. Use <a class="reference internal" href="init_config.html#c.PyConfig_Get" title="PyConfig_Get"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyConfig_Get("prefix")</span></code></a> (<a class="reference internal" href="../library/sys.html#sys.prefix" title="sys.prefix"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.prefix</span></code></a>) if <a class="reference internal" href="../library/venv.html#venv-def"><span class="std std-ref">virtual environments</span></a> need to be handled.</p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_GetExecPrefix">
<span class="n"><span class="pre">wchar_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">Py_GetExecPrefix</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_GetExecPrefix" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Return the <em>exec-prefix</em> for installed platform-<em>dependent</em> files. This is
derived through a number of complicated rules from the program name set with
<a class="reference internal" href="init_config.html#c.PyConfig.program_name" title="PyConfig.program_name"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.program_name</span></code></a> and some environment variables; for example, if the
program name is <code class="docutils literal notranslate"><span class="pre">'/usr/local/bin/python'</span></code>, the exec-prefix is
<code class="docutils literal notranslate"><span class="pre">'/usr/local'</span></code>. The returned string points into static storage; the caller
should not modify its value. This corresponds to the <strong class="makevar">exec_prefix</strong>
variable in the top-level <code class="file docutils literal notranslate"><span class="pre">Makefile</span></code> and the <code class="docutils literal notranslate"><span class="pre">--exec-prefix</span></code>
argument to the <strong class="program">configure</strong> script at build time. The value is
available to Python code as <code class="docutils literal notranslate"><span class="pre">sys.base_exec_prefix</span></code>. It is only useful on
Unix.</p>
<p>Background: The exec-prefix differs from the prefix when platform dependent
files (such as executables and shared libraries) are installed in a different
directory tree. In a typical installation, platform dependent files may be
installed in the <code class="file docutils literal notranslate"><span class="pre">/usr/local/plat</span></code> subtree while platform independent may
be installed in <code class="file docutils literal notranslate"><span class="pre">/usr/local</span></code>.</p>
<p>Generally speaking, a platform is a combination of hardware and software
families, e.g. Sparc machines running the Solaris 2.x operating system are
considered the same platform, but Intel machines running Solaris 2.x are another
platform, and Intel machines running Linux are yet another platform. Different
major revisions of the same operating system generally also form different
platforms. Non-Unix operating systems are a different story; the installation
strategies on those systems are so different that the prefix and exec-prefix are
meaningless, and set to the empty string. Note that compiled Python bytecode
files are platform independent (but not independent from the Python version by
which they were compiled!).</p>
<p>System administrators will know how to configure the <strong class="program">mount</strong> or
<strong class="program">automount</strong> programs to share <code class="file docutils literal notranslate"><span class="pre">/usr/local</span></code> between platforms
while having <code class="file docutils literal notranslate"><span class="pre">/usr/local/plat</span></code> be a different filesystem for each
platform.</p>
<p>This function should not be called before <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a>, otherwise
it returns <code class="docutils literal notranslate"><span class="pre">NULL</span></code>.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.10: </span>It now returns <code class="docutils literal notranslate"><span class="pre">NULL</span></code> if called before <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a>.</p>
</div>
<div class="deprecated-removed">
<p><span class="versionmodified deprecated">Deprecated since version 3.13, will be removed in version 3.15: </span>Use <a class="reference internal" href="init_config.html#c.PyConfig_Get" title="PyConfig_Get"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyConfig_Get("base_exec_prefix")</span></code></a>
(<a class="reference internal" href="../library/sys.html#sys.base_exec_prefix" title="sys.base_exec_prefix"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.base_exec_prefix</span></code></a>) instead. Use
<a class="reference internal" href="init_config.html#c.PyConfig_Get" title="PyConfig_Get"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyConfig_Get("exec_prefix")</span></code></a>
(<a class="reference internal" href="../library/sys.html#sys.exec_prefix" title="sys.exec_prefix"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.exec_prefix</span></code></a>) if <a class="reference internal" href="../library/venv.html#venv-def"><span class="std std-ref">virtual environments</span></a> need
to be handled.</p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_GetProgramFullPath">
<span class="n"><span class="pre">wchar_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">Py_GetProgramFullPath</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_GetProgramFullPath" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p id="index-17">Return the full program name of the Python executable; this is computed as a
side-effect of deriving the default module search path from the program name
(set by <a class="reference internal" href="init_config.html#c.PyConfig.program_name" title="PyConfig.program_name"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.program_name</span></code></a>). The returned string points into
static storage; the caller should not modify its value. The value is available
to Python code as <code class="docutils literal notranslate"><span class="pre">sys.executable</span></code>.</p>
<p>This function should not be called before <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a>, otherwise
it returns <code class="docutils literal notranslate"><span class="pre">NULL</span></code>.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.10: </span>It now returns <code class="docutils literal notranslate"><span class="pre">NULL</span></code> if called before <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a>.</p>
</div>
<div class="deprecated-removed">
<p><span class="versionmodified deprecated">Deprecated since version 3.13, will be removed in version 3.15: </span>Use <a class="reference internal" href="init_config.html#c.PyConfig_Get" title="PyConfig_Get"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyConfig_Get("executable")</span></code></a>
(<a class="reference internal" href="../library/sys.html#sys.executable" title="sys.executable"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.executable</span></code></a>) instead.</p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_GetPath">
<span class="n"><span class="pre">wchar_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">Py_GetPath</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_GetPath" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p id="index-18">Return the default module search path; this is computed from the program name
(set by <a class="reference internal" href="init_config.html#c.PyConfig.program_name" title="PyConfig.program_name"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.program_name</span></code></a>) and some environment variables.
The returned string consists of a series of directory names separated by a
platform dependent delimiter character. The delimiter character is <code class="docutils literal notranslate"><span class="pre">':'</span></code>
on Unix and macOS, <code class="docutils literal notranslate"><span class="pre">';'</span></code> on Windows. The returned string points into
static storage; the caller should not modify its value. The list
<a class="reference internal" href="../library/sys.html#sys.path" title="sys.path"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path</span></code></a> is initialized with this value on interpreter startup; it
can be (and usually is) modified later to change the search path for loading
modules.</p>
<p>This function should not be called before <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a>, otherwise
it returns <code class="docutils literal notranslate"><span class="pre">NULL</span></code>.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.10: </span>It now returns <code class="docutils literal notranslate"><span class="pre">NULL</span></code> if called before <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a>.</p>
</div>
<div class="deprecated-removed">
<p><span class="versionmodified deprecated">Deprecated since version 3.13, will be removed in version 3.15: </span>Use <a class="reference internal" href="init_config.html#c.PyConfig_Get" title="PyConfig_Get"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyConfig_Get("module_search_paths")</span></code></a>
(<a class="reference internal" href="../library/sys.html#sys.path" title="sys.path"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path</span></code></a>) instead.</p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_GetVersion">
<span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">Py_GetVersion</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_GetVersion" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Return the version of this Python interpreter. This is a string that looks
something like</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="s">"3.0a5+ (py3k:63103M, May 12 2008, 00:53:55) </span><span class="se">\n</span><span class="s">[GCC 4.2.3]"</span>
</pre></div>
</div>
<p id="index-19">The first word (up to the first space character) is the current Python version;
the first characters are the major and minor version separated by a
period. The returned string points into static storage; the caller should not
modify its value. The value is available to Python code as <a class="reference internal" href="../library/sys.html#sys.version" title="sys.version"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.version</span></code></a>.</p>
<p>See also the <a class="reference internal" href="apiabiversion.html#c.Py_Version" title="Py_Version"><code class="xref c c-var docutils literal notranslate"><span class="pre">Py_Version</span></code></a> constant.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_GetPlatform">
<span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">Py_GetPlatform</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_GetPlatform" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p id="index-20">Return the platform identifier for the current platform. On Unix, this is
formed from the “official” name of the operating system, converted to lower
case, followed by the major revision number; e.g., for Solaris 2.x, which is
also known as SunOS 5.x, the value is <code class="docutils literal notranslate"><span class="pre">'sunos5'</span></code>. On macOS, it is
<code class="docutils literal notranslate"><span class="pre">'darwin'</span></code>. On Windows, it is <code class="docutils literal notranslate"><span class="pre">'win'</span></code>. The returned string points into
static storage; the caller should not modify its value. The value is available
to Python code as <code class="docutils literal notranslate"><span class="pre">sys.platform</span></code>.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_GetCopyright">
<span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">Py_GetCopyright</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_GetCopyright" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Return the official copyright string for the current Python version, for example</p>
<p><code class="docutils literal notranslate"><span class="pre">'Copyright</span> <span class="pre">1991-1995</span> <span class="pre">Stichting</span> <span class="pre">Mathematisch</span> <span class="pre">Centrum,</span> <span class="pre">Amsterdam'</span></code></p>
<p id="index-21">The returned string points into static storage; the caller should not modify its
value. The value is available to Python code as <code class="docutils literal notranslate"><span class="pre">sys.copyright</span></code>.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_GetCompiler">
<span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">Py_GetCompiler</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_GetCompiler" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Return an indication of the compiler used to build the current Python version,
in square brackets, for example:</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="s">"[GCC 2.7.2.2]"</span>
</pre></div>
</div>
<p id="index-22">The returned string points into static storage; the caller should not modify its
value. The value is available to Python code as part of the variable
<code class="docutils literal notranslate"><span class="pre">sys.version</span></code>.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_GetBuildInfo">
<span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">Py_GetBuildInfo</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_GetBuildInfo" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Return information about the sequence number and build date and time of the
current Python interpreter instance, for example</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="s">"#67, Aug 1 1997, 22:34:28"</span>
</pre></div>
</div>
<p id="index-23">The returned string points into static storage; the caller should not modify its
value. The value is available to Python code as part of the variable
<code class="docutils literal notranslate"><span class="pre">sys.version</span></code>.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PySys_SetArgvEx">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PySys_SetArgvEx</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">argc</span></span>, <span class="n"><span class="pre">wchar_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">argv</span></span>, <span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">updatepath</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PySys_SetArgvEx" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p id="index-24">This API is kept for backward compatibility: setting
<a class="reference internal" href="init_config.html#c.PyConfig.argv" title="PyConfig.argv"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.argv</span></code></a>, <a class="reference internal" href="init_config.html#c.PyConfig.parse_argv" title="PyConfig.parse_argv"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.parse_argv</span></code></a> and
<a class="reference internal" href="init_config.html#c.PyConfig.safe_path" title="PyConfig.safe_path"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.safe_path</span></code></a> should be used instead, see <a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python
Initialization Configuration</span></a>.</p>
<p>Set <a class="reference internal" href="../library/sys.html#sys.argv" title="sys.argv"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.argv</span></code></a> based on <em>argc</em> and <em>argv</em>. These parameters are
similar to those passed to the program’s <code class="xref c c-func docutils literal notranslate"><span class="pre">main()</span></code> function with the
difference that the first entry should refer to the script file to be
executed rather than the executable hosting the Python interpreter. If there
isn’t a script that will be run, the first entry in <em>argv</em> can be an empty
string. If this function fails to initialize <a class="reference internal" href="../library/sys.html#sys.argv" title="sys.argv"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.argv</span></code></a>, a fatal
condition is signalled using <a class="reference internal" href="sys.html#c.Py_FatalError" title="Py_FatalError"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_FatalError()</span></code></a>.</p>
<p>If <em>updatepath</em> is zero, this is all the function does. If <em>updatepath</em>
is non-zero, the function also modifies <a class="reference internal" href="../library/sys.html#sys.path" title="sys.path"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path</span></code></a> according to the
following algorithm:</p>
<ul class="simple">
<li><p>If the name of an existing script is passed in <code class="docutils literal notranslate"><span class="pre">argv[0]</span></code>, the absolute
path of the directory where the script is located is prepended to
<a class="reference internal" href="../library/sys.html#sys.path" title="sys.path"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path</span></code></a>.</p></li>
<li><p>Otherwise (that is, if <em>argc</em> is <code class="docutils literal notranslate"><span class="pre">0</span></code> or <code class="docutils literal notranslate"><span class="pre">argv[0]</span></code> doesn’t point
to an existing file name), an empty string is prepended to
<a class="reference internal" href="../library/sys.html#sys.path" title="sys.path"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path</span></code></a>, which is the same as prepending the current working
directory (<code class="docutils literal notranslate"><span class="pre">"."</span></code>).</p></li>
</ul>
<p>Use <a class="reference internal" href="sys.html#c.Py_DecodeLocale" title="Py_DecodeLocale"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_DecodeLocale()</span></code></a> to decode a bytes string to get a
<span class="c-expr sig sig-inline c"><span class="n">wchar_t</span><span class="p">*</span></span> string.</p>
<p>See also <a class="reference internal" href="init_config.html#c.PyConfig.orig_argv" title="PyConfig.orig_argv"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.orig_argv</span></code></a> and <a class="reference internal" href="init_config.html#c.PyConfig.argv" title="PyConfig.argv"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.argv</span></code></a>
members of the <a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python Initialization Configuration</span></a>.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>It is recommended that applications embedding the Python interpreter
for purposes other than executing a single script pass <code class="docutils literal notranslate"><span class="pre">0</span></code> as <em>updatepath</em>,
and update <a class="reference internal" href="../library/sys.html#sys.path" title="sys.path"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path</span></code></a> themselves if desired.
See <span class="target" id="index-25"></span><a class="cve reference external" href="https://www.cve.org/CVERecord?id=CVE-2008-5983"><strong>CVE 2008-5983</strong></a>.</p>
<p>On versions before 3.1.3, you can achieve the same effect by manually
popping the first <a class="reference internal" href="../library/sys.html#sys.path" title="sys.path"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path</span></code></a> element after having called
<a class="reference internal" href="#c.PySys_SetArgv" title="PySys_SetArgv"><code class="xref c c-func docutils literal notranslate"><span class="pre">PySys_SetArgv()</span></code></a>, for example using:</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="n">PyRun_SimpleString</span><span class="p">(</span><span class="s">"import sys; sys.path.pop(0)</span><span class="se">\n</span><span class="s">"</span><span class="p">);</span>
</pre></div>
</div>
</div>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.1.3.</span></p>
</div>
<div class="deprecated-removed">
<p><span class="versionmodified deprecated">Deprecated since version 3.11, will be removed in version 3.15.</span></p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PySys_SetArgv">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PySys_SetArgv</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">argc</span></span>, <span class="n"><span class="pre">wchar_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">argv</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PySys_SetArgv" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>This API is kept for backward compatibility: setting
<a class="reference internal" href="init_config.html#c.PyConfig.argv" title="PyConfig.argv"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.argv</span></code></a> and <a class="reference internal" href="init_config.html#c.PyConfig.parse_argv" title="PyConfig.parse_argv"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.parse_argv</span></code></a> should be used
instead, see <a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python Initialization Configuration</span></a>.</p>
<p>This function works like <a class="reference internal" href="#c.PySys_SetArgvEx" title="PySys_SetArgvEx"><code class="xref c c-func docutils literal notranslate"><span class="pre">PySys_SetArgvEx()</span></code></a> with <em>updatepath</em> set
to <code class="docutils literal notranslate"><span class="pre">1</span></code> unless the <strong class="program">python</strong> interpreter was started with the
<a class="reference internal" href="../using/cmdline.html#cmdoption-I"><code class="xref std std-option docutils literal notranslate"><span class="pre">-I</span></code></a>.</p>
<p>Use <a class="reference internal" href="sys.html#c.Py_DecodeLocale" title="Py_DecodeLocale"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_DecodeLocale()</span></code></a> to decode a bytes string to get a
<span class="c-expr sig sig-inline c"><span class="n">wchar_t</span><span class="p">*</span></span> string.</p>
<p>See also <a class="reference internal" href="init_config.html#c.PyConfig.orig_argv" title="PyConfig.orig_argv"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.orig_argv</span></code></a> and <a class="reference internal" href="init_config.html#c.PyConfig.argv" title="PyConfig.argv"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.argv</span></code></a>
members of the <a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python Initialization Configuration</span></a>.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.4: </span>The <em>updatepath</em> value depends on <a class="reference internal" href="../using/cmdline.html#cmdoption-I"><code class="xref std std-option docutils literal notranslate"><span class="pre">-I</span></code></a>.</p>
</div>
<div class="deprecated-removed">
<p><span class="versionmodified deprecated">Deprecated since version 3.11, will be removed in version 3.15.</span></p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_SetPythonHome">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_SetPythonHome</span></span></span><span class="sig-paren">(</span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="n"><span class="pre">wchar_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">home</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_SetPythonHome" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>This API is kept for backward compatibility: setting
<a class="reference internal" href="init_config.html#c.PyConfig.home" title="PyConfig.home"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.home</span></code></a> should be used instead, see <a class="reference internal" href="init_config.html#init-config"><span class="std std-ref">Python
Initialization Configuration</span></a>.</p>
<p>Set the default “home” directory, that is, the location of the standard
Python libraries. See <span class="target" id="index-26"></span><a class="reference internal" href="../using/cmdline.html#envvar-PYTHONHOME"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONHOME</span></code></a> for the meaning of the
argument string.</p>
<p>The argument should point to a zero-terminated character string in static
storage whose contents will not change for the duration of the program’s
execution. No code in the Python interpreter will change the contents of
this storage.</p>
<p>Use <a class="reference internal" href="sys.html#c.Py_DecodeLocale" title="Py_DecodeLocale"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_DecodeLocale()</span></code></a> to decode a bytes string to get a
<span class="c-expr sig sig-inline c"><span class="n">wchar_t</span><span class="p">*</span></span> string.</p>
<div class="deprecated-removed">
<p><span class="versionmodified deprecated">Deprecated since version 3.11, will be removed in version 3.15.</span></p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_GetPythonHome">
<span class="n"><span class="pre">wchar_t</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">Py_GetPythonHome</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_GetPythonHome" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Return the default “home”, that is, the value set by
<a class="reference internal" href="init_config.html#c.PyConfig.home" title="PyConfig.home"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyConfig.home</span></code></a>, or the value of the <span class="target" id="index-27"></span><a class="reference internal" href="../using/cmdline.html#envvar-PYTHONHOME"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONHOME</span></code></a>
environment variable if it is set.</p>
<p>This function should not be called before <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a>, otherwise
it returns <code class="docutils literal notranslate"><span class="pre">NULL</span></code>.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.10: </span>It now returns <code class="docutils literal notranslate"><span class="pre">NULL</span></code> if called before <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a>.</p>
</div>
<div class="deprecated-removed">
<p><span class="versionmodified deprecated">Deprecated since version 3.13, will be removed in version 3.15: </span>Use <a class="reference internal" href="init_config.html#c.PyConfig_Get" title="PyConfig_Get"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyConfig_Get("home")</span></code></a> or the
<span class="target" id="index-28"></span><a class="reference internal" href="../using/cmdline.html#envvar-PYTHONHOME"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONHOME</span></code></a> environment variable instead.</p>
</div>
</dd></dl>
</section>
<section id="thread-state-and-the-global-interpreter-lock">
<span id="threads"></span><h2>Thread State and the Global Interpreter Lock<a class="headerlink" href="#thread-state-and-the-global-interpreter-lock" title="Link to this heading">¶</a></h2>
<p id="index-29">Unless on a <a class="reference internal" href="../glossary.html#term-free-threading"><span class="xref std std-term">free-threaded</span></a> build of <a class="reference internal" href="../glossary.html#term-CPython"><span class="xref std std-term">CPython</span></a>,
the Python interpreter is not fully thread-safe. In order to support
multi-threaded Python programs, there’s a global lock, called the <a class="reference internal" href="../glossary.html#term-global-interpreter-lock"><span class="xref std std-term">global
interpreter lock</span></a> or <a class="reference internal" href="../glossary.html#term-GIL"><span class="xref std std-term">GIL</span></a>, that must be held by the current thread before
it can safely access Python objects. Without the lock, even the simplest
operations could cause problems in a multi-threaded program: for example, when
two threads simultaneously increment the reference count of the same object, the
reference count could end up being incremented only once instead of twice.</p>
<p id="index-30">Therefore, the rule exists that only the thread that has acquired the
<a class="reference internal" href="../glossary.html#term-GIL"><span class="xref std std-term">GIL</span></a> may operate on Python objects or call Python/C API functions.
In order to emulate concurrency of execution, the interpreter regularly
tries to switch threads (see <a class="reference internal" href="../library/sys.html#sys.setswitchinterval" title="sys.setswitchinterval"><code class="xref py py-func docutils literal notranslate"><span class="pre">sys.setswitchinterval()</span></code></a>). The lock is also
released around potentially blocking I/O operations like reading or writing
a file, so that other Python threads can run in the meantime.</p>
<p id="index-31">The Python interpreter keeps some thread-specific bookkeeping information
inside a data structure called <a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyThreadState</span></code></a>, known as a <a class="reference internal" href="../glossary.html#term-thread-state"><span class="xref std std-term">thread state</span></a>.
Each OS thread has a thread-local pointer to a <a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyThreadState</span></code></a>; a thread state
referenced by this pointer is considered to be <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached</span></a>.</p>
<p>A thread can only have one <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a> at a time. An attached
thread state is typically analogous with holding the <a class="reference internal" href="../glossary.html#term-GIL"><span class="xref std std-term">GIL</span></a>, except on
<a class="reference internal" href="../glossary.html#term-free-threading"><span class="xref std std-term">free-threaded</span></a> builds. On builds with the <a class="reference internal" href="../glossary.html#term-GIL"><span class="xref std std-term">GIL</span></a> enabled,
<a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attaching</span></a> a thread state will block until the <a class="reference internal" href="../glossary.html#term-GIL"><span class="xref std std-term">GIL</span></a>
can be acquired. However, even on builds with the <a class="reference internal" href="../glossary.html#term-GIL"><span class="xref std std-term">GIL</span></a> disabled, it is still required
to have an attached thread state to call most of the C API.</p>
<p>In general, there will always be an <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a> when using Python’s C API.
Only in some specific cases (such as in a <a class="reference internal" href="#c.Py_BEGIN_ALLOW_THREADS" title="Py_BEGIN_ALLOW_THREADS"><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_BEGIN_ALLOW_THREADS</span></code></a> block) will the
thread not have an attached thread state. If uncertain, check if <a class="reference internal" href="#c.PyThreadState_GetUnchecked" title="PyThreadState_GetUnchecked"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyThreadState_GetUnchecked()</span></code></a> returns
<code class="docutils literal notranslate"><span class="pre">NULL</span></code>.</p>
<section id="detaching-the-thread-state-from-extension-code">
<h3>Detaching the thread state from extension code<a class="headerlink" href="#detaching-the-thread-state-from-extension-code" title="Link to this heading">¶</a></h3>
<p>Most extension code manipulating the <a class="reference internal" href="../glossary.html#term-thread-state"><span class="xref std std-term">thread state</span></a> has the following simple
structure:</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="n">Save</span><span class="w"> </span><span class="n">the</span><span class="w"> </span><span class="kr">thread</span><span class="w"> </span><span class="n">state</span><span class="w"> </span><span class="n">in</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="n">local</span><span class="w"> </span><span class="n">variable</span><span class="p">.</span>
<span class="p">...</span><span class="w"> </span><span class="n">Do</span><span class="w"> </span><span class="n">some</span><span class="w"> </span><span class="n">blocking</span><span class="w"> </span><span class="n">I</span><span class="o">/</span><span class="n">O</span><span class="w"> </span><span class="n">operation</span><span class="w"> </span><span class="p">...</span>
<span class="n">Restore</span><span class="w"> </span><span class="n">the</span><span class="w"> </span><span class="kr">thread</span><span class="w"> </span><span class="n">state</span><span class="w"> </span><span class="n">from</span><span class="w"> </span><span class="n">the</span><span class="w"> </span><span class="n">local</span><span class="w"> </span><span class="n">variable</span><span class="p">.</span>
</pre></div>
</div>
<p>This is so common that a pair of macros exists to simplify it:</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="n">Py_BEGIN_ALLOW_THREADS</span>
<span class="p">...</span><span class="w"> </span><span class="n">Do</span><span class="w"> </span><span class="n">some</span><span class="w"> </span><span class="n">blocking</span><span class="w"> </span><span class="n">I</span><span class="o">/</span><span class="n">O</span><span class="w"> </span><span class="n">operation</span><span class="w"> </span><span class="p">...</span>
<span class="n">Py_END_ALLOW_THREADS</span>
</pre></div>
</div>
<p id="index-32">The <a class="reference internal" href="#c.Py_BEGIN_ALLOW_THREADS" title="Py_BEGIN_ALLOW_THREADS"><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_BEGIN_ALLOW_THREADS</span></code></a> macro opens a new block and declares a
hidden local variable; the <a class="reference internal" href="#c.Py_END_ALLOW_THREADS" title="Py_END_ALLOW_THREADS"><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_END_ALLOW_THREADS</span></code></a> macro closes the
block.</p>
<p>The block above expands to the following code:</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="n">PyThreadState</span><span class="w"> </span><span class="o">*</span><span class="n">_save</span><span class="p">;</span>
<span class="n">_save</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">PyEval_SaveThread</span><span class="p">();</span>
<span class="p">...</span><span class="w"> </span><span class="n">Do</span><span class="w"> </span><span class="n">some</span><span class="w"> </span><span class="n">blocking</span><span class="w"> </span><span class="n">I</span><span class="o">/</span><span class="n">O</span><span class="w"> </span><span class="n">operation</span><span class="w"> </span><span class="p">...</span>
<span class="n">PyEval_RestoreThread</span><span class="p">(</span><span class="n">_save</span><span class="p">);</span>
</pre></div>
</div>
<p id="index-33">Here is how these functions work:</p>
<p>The <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a> holds the <a class="reference internal" href="../glossary.html#term-GIL"><span class="xref std std-term">GIL</span></a> for the entire interpreter. When detaching
the <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a>, the <a class="reference internal" href="../glossary.html#term-GIL"><span class="xref std std-term">GIL</span></a> is released, allowing other threads to attach
a thread state to their own thread, thus getting the <a class="reference internal" href="../glossary.html#term-GIL"><span class="xref std std-term">GIL</span></a> and can start executing.
The pointer to the prior <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a> is stored as a local variable.
Upon reaching <a class="reference internal" href="#c.Py_END_ALLOW_THREADS" title="Py_END_ALLOW_THREADS"><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_END_ALLOW_THREADS</span></code></a>, the thread state that was
previously <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached</span></a> is passed to <a class="reference internal" href="#c.PyEval_RestoreThread" title="PyEval_RestoreThread"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyEval_RestoreThread()</span></code></a>.
This function will block until another releases its <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">thread state</span></a>,
thus allowing the old <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">thread state</span></a> to get re-attached and the
C API can be called again.</p>
<p>For <a class="reference internal" href="../glossary.html#term-free-threading"><span class="xref std std-term">free-threaded</span></a> builds, the <a class="reference internal" href="../glossary.html#term-GIL"><span class="xref std std-term">GIL</span></a> is normally
out of the question, but detaching the <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">thread state</span></a> is still required
for blocking I/O and long operations. The difference is that threads don’t have to wait for the <a class="reference internal" href="../glossary.html#term-GIL"><span class="xref std std-term">GIL</span></a>
to be released to attach their thread state, allowing true multi-core parallelism.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>Calling system I/O functions is the most common use case for detaching
the <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">thread state</span></a>, but it can also be useful before calling
long-running computations which don’t need access to Python objects, such
as compression or cryptographic functions operating over memory buffers.
For example, the standard <a class="reference internal" href="../library/zlib.html#module-zlib" title="zlib: Low-level interface to compression and decompression routines compatible with gzip."><code class="xref py py-mod docutils literal notranslate"><span class="pre">zlib</span></code></a> and <a class="reference internal" href="../library/hashlib.html#module-hashlib" title="hashlib: Secure hash and message digest algorithms."><code class="xref py py-mod docutils literal notranslate"><span class="pre">hashlib</span></code></a> modules detach the
<a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">thread state</span></a> when compressing or hashing data.</p>
</div>
</section>
<section id="non-python-created-threads">
<span id="gilstate"></span><h3>Non-Python created threads<a class="headerlink" href="#non-python-created-threads" title="Link to this heading">¶</a></h3>
<p>When threads are created using the dedicated Python APIs (such as the
<a class="reference internal" href="../library/threading.html#module-threading" title="threading: Thread-based parallelism."><code class="xref py py-mod docutils literal notranslate"><span class="pre">threading</span></code></a> module), a thread state is automatically associated to them
and the code showed above is therefore correct. However, when threads are
created from C (for example by a third-party library with its own thread
management), they don’t hold the <a class="reference internal" href="../glossary.html#term-GIL"><span class="xref std std-term">GIL</span></a>, because they don’t have an
<a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a>.</p>
<p>If you need to call Python code from these threads (often this will be part
of a callback API provided by the aforementioned third-party library),
you must first register these threads with the interpreter by
creating an <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a> before you can start using the Python/C
API. When you are done, you should detach the <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">thread state</span></a>, and
finally free it.</p>
<p>The <a class="reference internal" href="#c.PyGILState_Ensure" title="PyGILState_Ensure"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyGILState_Ensure()</span></code></a> and <a class="reference internal" href="#c.PyGILState_Release" title="PyGILState_Release"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyGILState_Release()</span></code></a> functions do
all of the above automatically. The typical idiom for calling into Python
from a C thread is:</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="n">PyGILState_STATE</span><span class="w"> </span><span class="n">gstate</span><span class="p">;</span>
<span class="n">gstate</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">PyGILState_Ensure</span><span class="p">();</span>
<span class="cm">/* Perform Python actions here. */</span>
<span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">CallSomeFunction</span><span class="p">();</span>
<span class="cm">/* evaluate result or handle exception */</span>
<span class="cm">/* Release the thread. No Python API allowed beyond this point. */</span>
<span class="n">PyGILState_Release</span><span class="p">(</span><span class="n">gstate</span><span class="p">);</span>
</pre></div>
</div>
<p>Note that the <code class="docutils literal notranslate"><span class="pre">PyGILState_*</span></code> functions assume there is only one global
interpreter (created automatically by <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a>). Python
supports the creation of additional interpreters (using
<a class="reference internal" href="#c.Py_NewInterpreter" title="Py_NewInterpreter"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_NewInterpreter()</span></code></a>), but mixing multiple interpreters and the
<code class="docutils literal notranslate"><span class="pre">PyGILState_*</span></code> API is unsupported. This is because <a class="reference internal" href="#c.PyGILState_Ensure" title="PyGILState_Ensure"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyGILState_Ensure()</span></code></a>
and similar functions default to <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attaching</span></a> a
<a class="reference internal" href="../glossary.html#term-thread-state"><span class="xref std std-term">thread state</span></a> for the main interpreter, meaning that the thread can’t safely
interact with the calling subinterpreter.</p>
</section>
<section id="supporting-subinterpreters-in-non-python-threads">
<h3>Supporting subinterpreters in non-Python threads<a class="headerlink" href="#supporting-subinterpreters-in-non-python-threads" title="Link to this heading">¶</a></h3>
<p>If you would like to support subinterpreters with non-Python created threads, you
must use the <code class="docutils literal notranslate"><span class="pre">PyThreadState_*</span></code> API instead of the traditional <code class="docutils literal notranslate"><span class="pre">PyGILState_*</span></code>
API.</p>
<p>In particular, you must store the interpreter state from the calling
function and pass it to <a class="reference internal" href="#c.PyThreadState_New" title="PyThreadState_New"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyThreadState_New()</span></code></a>, which will ensure that
the <a class="reference internal" href="../glossary.html#term-thread-state"><span class="xref std std-term">thread state</span></a> is targeting the correct interpreter:</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="cm">/* The return value of PyInterpreterState_Get() from the</span>
<span class="cm"> function that created this thread. */</span>
<span class="n">PyInterpreterState</span><span class="w"> </span><span class="o">*</span><span class="n">interp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ThreadData</span><span class="o">-></span><span class="n">interp</span><span class="p">;</span>
<span class="n">PyThreadState</span><span class="w"> </span><span class="o">*</span><span class="n">tstate</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">PyThreadState_New</span><span class="p">(</span><span class="n">interp</span><span class="p">);</span>
<span class="n">PyThreadState_Swap</span><span class="p">(</span><span class="n">tstate</span><span class="p">);</span>
<span class="cm">/* GIL of the subinterpreter is now held.</span>
<span class="cm"> Perform Python actions here. */</span>
<span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">CallSomeFunction</span><span class="p">();</span>
<span class="cm">/* evaluate result or handle exception */</span>
<span class="cm">/* Destroy the thread state. No Python API allowed beyond this point. */</span>
<span class="n">PyThreadState_Clear</span><span class="p">(</span><span class="n">tstate</span><span class="p">);</span>
<span class="n">PyThreadState_DeleteCurrent</span><span class="p">();</span>
</pre></div>
</div>
</section>
<section id="cautions-about-fork">
<span id="fork-and-threads"></span><h3>Cautions about fork()<a class="headerlink" href="#cautions-about-fork" title="Link to this heading">¶</a></h3>
<p>Another important thing to note about threads is their behaviour in the face
of the C <code class="xref c c-func docutils literal notranslate"><span class="pre">fork()</span></code> call. On most systems with <code class="xref c c-func docutils literal notranslate"><span class="pre">fork()</span></code>, after a
process forks only the thread that issued the fork will exist. This has a
concrete impact both on how locks must be handled and on all stored state
in CPython’s runtime.</p>
<p>The fact that only the “current” thread remains
means any locks held by other threads will never be released. Python solves
this for <a class="reference internal" href="../library/os.html#os.fork" title="os.fork"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.fork()</span></code></a> by acquiring the locks it uses internally before
the fork, and releasing them afterwards. In addition, it resets any
<a class="reference internal" href="../library/threading.html#lock-objects"><span class="std std-ref">Lock objects</span></a> in the child. When extending or embedding Python, there
is no way to inform Python of additional (non-Python) locks that need to be
acquired before or reset after a fork. OS facilities such as
<code class="xref c c-func docutils literal notranslate"><span class="pre">pthread_atfork()</span></code> would need to be used to accomplish the same thing.
Additionally, when extending or embedding Python, calling <code class="xref c c-func docutils literal notranslate"><span class="pre">fork()</span></code>
directly rather than through <a class="reference internal" href="../library/os.html#os.fork" title="os.fork"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.fork()</span></code></a> (and returning to or calling
into Python) may result in a deadlock by one of Python’s internal locks
being held by a thread that is defunct after the fork.
<a class="reference internal" href="sys.html#c.PyOS_AfterFork_Child" title="PyOS_AfterFork_Child"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyOS_AfterFork_Child()</span></code></a> tries to reset the necessary locks, but is not
always able to.</p>
<p>The fact that all other threads go away also means that CPython’s
runtime state there must be cleaned up properly, which <a class="reference internal" href="../library/os.html#os.fork" title="os.fork"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.fork()</span></code></a>
does. This means finalizing all other <a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyThreadState</span></code></a> objects
belonging to the current interpreter and all other
<a class="reference internal" href="#c.PyInterpreterState" title="PyInterpreterState"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyInterpreterState</span></code></a> objects. Due to this and the special
nature of the <a class="reference internal" href="#sub-interpreter-support"><span class="std std-ref">“main” interpreter</span></a>,
<code class="xref c c-func docutils literal notranslate"><span class="pre">fork()</span></code> should only be called in that interpreter’s “main”
thread, where the CPython global runtime was originally initialized.
The only exception is if <code class="xref c c-func docutils literal notranslate"><span class="pre">exec()</span></code> will be called immediately
after.</p>
</section>
<section id="cautions-regarding-runtime-finalization">
<span id="id1"></span><h3>Cautions regarding runtime finalization<a class="headerlink" href="#cautions-regarding-runtime-finalization" title="Link to this heading">¶</a></h3>
<p>In the late stage of <a class="reference internal" href="../glossary.html#term-interpreter-shutdown"><span class="xref std std-term">interpreter shutdown</span></a>, after attempting to wait for
non-daemon threads to exit (though this can be interrupted by
<a class="reference internal" href="../library/exceptions.html#KeyboardInterrupt" title="KeyboardInterrupt"><code class="xref py py-class docutils literal notranslate"><span class="pre">KeyboardInterrupt</span></code></a>) and running the <a class="reference internal" href="../library/atexit.html#module-atexit" title="atexit: Register and execute cleanup functions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">atexit</span></code></a> functions, the runtime
is marked as <em>finalizing</em>: <a class="reference internal" href="#c.Py_IsFinalizing" title="Py_IsFinalizing"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_IsFinalizing()</span></code></a> and
<a class="reference internal" href="../library/sys.html#sys.is_finalizing" title="sys.is_finalizing"><code class="xref py py-func docutils literal notranslate"><span class="pre">sys.is_finalizing()</span></code></a> return true. At this point, only the <em>finalization
thread</em> that initiated finalization (typically the main thread) is allowed to
acquire the <a class="reference internal" href="../glossary.html#term-GIL"><span class="xref std std-term">GIL</span></a>.</p>
<p>If any thread, other than the finalization thread, attempts to attach a <a class="reference internal" href="../glossary.html#term-thread-state"><span class="xref std std-term">thread state</span></a>
during finalization, either explicitly or
implicitly, the thread enters <strong>a permanently blocked state</strong>
where it remains until the program exits. In most cases this is harmless, but this can result
in deadlock if a later stage of finalization attempts to acquire a lock owned by the
blocked thread, or otherwise waits on the blocked thread.</p>
<p>Gross? Yes. This prevents random crashes and/or unexpectedly skipped C++
finalizations further up the call stack when such threads were forcibly exited
here in CPython 3.13 and earlier. The CPython runtime <a class="reference internal" href="../glossary.html#term-thread-state"><span class="xref std std-term">thread state</span></a> C APIs
have never had any error reporting or handling expectations at <a class="reference internal" href="../glossary.html#term-thread-state"><span class="xref std std-term">thread state</span></a>
attachment time that would’ve allowed for graceful exit from this situation. Changing that
would require new stable C APIs and rewriting the majority of C code in the
CPython ecosystem to use those with error handling.</p>
</section>
<section id="high-level-api">
<h3>High-level API<a class="headerlink" href="#high-level-api" title="Link to this heading">¶</a></h3>
<p>These are the most commonly used types and functions when writing C extension
code, or when embedding the Python interpreter:</p>
<dl class="c type">
<dt class="sig sig-object c" id="c.PyInterpreterState">
<span class="k"><span class="pre">type</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyInterpreterState</span></span></span><a class="headerlink" href="#c.PyInterpreterState" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Limited API</span></a> (as an opaque struct).</em><p>This data structure represents the state shared by a number of cooperating
threads. Threads belonging to the same interpreter share their module
administration and a few other internal items. There are no public members in
this structure.</p>
<p>Threads belonging to different interpreters initially share nothing, except
process state like available memory, open file descriptors and such. The global
interpreter lock is also shared by all threads, regardless of to which
interpreter they belong.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.12: </span><span class="target" id="index-34"></span><a class="pep reference external" href="https://peps.python.org/pep-0684/"><strong>PEP 684</strong></a> introduced the possibility
of a <a class="reference internal" href="#per-interpreter-gil"><span class="std std-ref">per-interpreter GIL</span></a>.
See <a class="reference internal" href="#c.Py_NewInterpreterFromConfig" title="Py_NewInterpreterFromConfig"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_NewInterpreterFromConfig()</span></code></a>.</p>
</div>
</dd></dl>
<dl class="c type">
<dt class="sig sig-object c" id="c.PyThreadState">
<span class="k"><span class="pre">type</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyThreadState</span></span></span><a class="headerlink" href="#c.PyThreadState" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Limited API</span></a> (as an opaque struct).</em><p>This data structure represents the state of a single thread. The only public
data member is:</p>
<dl class="c member">
<dt class="sig sig-object c" id="c.PyThreadState.interp">
<a class="reference internal" href="#c.PyInterpreterState" title="PyInterpreterState"><span class="n"><span class="pre">PyInterpreterState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">interp</span></span></span><a class="headerlink" href="#c.PyThreadState.interp" title="Link to this definition">¶</a><br /></dt>
<dd><p>This thread’s interpreter state.</p>
</dd></dl>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyEval_InitThreads">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyEval_InitThreads</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyEval_InitThreads" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p id="index-35">Deprecated function which does nothing.</p>
<p>In Python 3.6 and older, this function created the GIL if it didn’t exist.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.9: </span>The function now does nothing.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.7: </span>This function is now called by <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a>, so you don’t
have to call it yourself anymore.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.2: </span>This function cannot be called before <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a> anymore.</p>
</div>
<div class="deprecated">
<p><span class="versionmodified deprecated">Deprecated since version 3.9.</span></p>
</div>
<span class="target" id="index-36"></span></dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyEval_SaveThread">
<a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><span class="n"><span class="pre">PyThreadState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">PyEval_SaveThread</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyEval_SaveThread" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Detach the <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a> and return it.
The thread will have no <a class="reference internal" href="../glossary.html#term-thread-state"><span class="xref std std-term">thread state</span></a> upon returning.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyEval_RestoreThread">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyEval_RestoreThread</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><span class="n"><span class="pre">PyThreadState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">tstate</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyEval_RestoreThread" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Set the <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a> to <em>tstate</em>.
The passed <a class="reference internal" href="../glossary.html#term-thread-state"><span class="xref std std-term">thread state</span></a> <strong>should not</strong> be <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached</span></a>,
otherwise deadlock ensues. <em>tstate</em> will be attached upon returning.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>Calling this function from a thread when the runtime is finalizing will
hang the thread until the program exits, even if the thread was not
created by Python. Refer to
<a class="reference internal" href="#cautions-regarding-runtime-finalization"><span class="std std-ref">Cautions regarding runtime finalization</span></a> for more details.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.14: </span>Hangs the current thread, rather than terminating it, if called while the
interpreter is finalizing.</p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyThreadState_Get">
<a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><span class="n"><span class="pre">PyThreadState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">PyThreadState_Get</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyThreadState_Get" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Return the <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a>. If the thread has no attached
thread state, (such as when inside of <a class="reference internal" href="#c.Py_BEGIN_ALLOW_THREADS" title="Py_BEGIN_ALLOW_THREADS"><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_BEGIN_ALLOW_THREADS</span></code></a>
block), then this issues a fatal error (so that the caller needn’t check
for <code class="docutils literal notranslate"><span class="pre">NULL</span></code>).</p>
<p>See also <a class="reference internal" href="#c.PyThreadState_GetUnchecked" title="PyThreadState_GetUnchecked"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyThreadState_GetUnchecked()</span></code></a>.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyThreadState_GetUnchecked">
<a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><span class="n"><span class="pre">PyThreadState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">PyThreadState_GetUnchecked</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyThreadState_GetUnchecked" title="Link to this definition">¶</a><br /></dt>
<dd><p>Similar to <a class="reference internal" href="#c.PyThreadState_Get" title="PyThreadState_Get"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyThreadState_Get()</span></code></a>, but don’t kill the process with a
fatal error if it is NULL. The caller is responsible to check if the result
is NULL.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.13: </span>In Python 3.5 to 3.12, the function was private and known as
<code class="docutils literal notranslate"><span class="pre">_PyThreadState_UncheckedGet()</span></code>.</p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyThreadState_Swap">
<a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><span class="n"><span class="pre">PyThreadState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">PyThreadState_Swap</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><span class="n"><span class="pre">PyThreadState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">tstate</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyThreadState_Swap" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Set the <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a> to <em>tstate</em>, and return the
<a class="reference internal" href="../glossary.html#term-thread-state"><span class="xref std std-term">thread state</span></a> that was attached prior to calling.</p>
<p>This function is safe to call without an <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a>; it
will simply return <code class="docutils literal notranslate"><span class="pre">NULL</span></code> indicating that there was no prior thread state.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>Similar to <a class="reference internal" href="#c.PyGILState_Ensure" title="PyGILState_Ensure"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyGILState_Ensure()</span></code></a>, this function will hang the
thread if the runtime is finalizing.</p>
</div>
</dd></dl>
<p>The following functions use thread-local storage, and are not compatible
with sub-interpreters:</p>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyGILState_Ensure">
<span class="n"><span class="pre">PyGILState_STATE</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyGILState_Ensure</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyGILState_Ensure" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Ensure that the current thread is ready to call the Python C API regardless
of the current state of Python, or of the <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a>. This may
be called as many times as desired by a thread as long as each call is
matched with a call to <a class="reference internal" href="#c.PyGILState_Release" title="PyGILState_Release"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyGILState_Release()</span></code></a>. In general, other
thread-related APIs may be used between <a class="reference internal" href="#c.PyGILState_Ensure" title="PyGILState_Ensure"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyGILState_Ensure()</span></code></a> and
<a class="reference internal" href="#c.PyGILState_Release" title="PyGILState_Release"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyGILState_Release()</span></code></a> calls as long as the thread state is restored to
its previous state before the Release(). For example, normal usage of the
<a class="reference internal" href="#c.Py_BEGIN_ALLOW_THREADS" title="Py_BEGIN_ALLOW_THREADS"><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_BEGIN_ALLOW_THREADS</span></code></a> and <a class="reference internal" href="#c.Py_END_ALLOW_THREADS" title="Py_END_ALLOW_THREADS"><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_END_ALLOW_THREADS</span></code></a> macros is
acceptable.</p>
<p>The return value is an opaque “handle” to the <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a> when
<a class="reference internal" href="#c.PyGILState_Ensure" title="PyGILState_Ensure"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyGILState_Ensure()</span></code></a> was called, and must be passed to
<a class="reference internal" href="#c.PyGILState_Release" title="PyGILState_Release"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyGILState_Release()</span></code></a> to ensure Python is left in the same state. Even
though recursive calls are allowed, these handles <em>cannot</em> be shared - each
unique call to <a class="reference internal" href="#c.PyGILState_Ensure" title="PyGILState_Ensure"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyGILState_Ensure()</span></code></a> must save the handle for its call
to <a class="reference internal" href="#c.PyGILState_Release" title="PyGILState_Release"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyGILState_Release()</span></code></a>.</p>
<p>When the function returns, there will be an <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a>
and the thread will be able to call arbitrary Python code. Failure is a fatal error.</p>
<div class="admonition warning">
<p class="admonition-title">Warning</p>
<p>Calling this function when the runtime is finalizing is unsafe. Doing
so will either hang the thread until the program ends, or fully crash
the interpreter in rare cases. Refer to
<a class="reference internal" href="#cautions-regarding-runtime-finalization"><span class="std std-ref">Cautions regarding runtime finalization</span></a> for more details.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.14: </span>Hangs the current thread, rather than terminating it, if called while the
interpreter is finalizing.</p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyGILState_Release">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyGILState_Release</span></span></span><span class="sig-paren">(</span><span class="n"><span class="pre">PyGILState_STATE</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyGILState_Release" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Release any resources previously acquired. After this call, Python’s state will
be the same as it was prior to the corresponding <a class="reference internal" href="#c.PyGILState_Ensure" title="PyGILState_Ensure"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyGILState_Ensure()</span></code></a> call
(but generally this state will be unknown to the caller, hence the use of the
GILState API).</p>
<p>Every call to <a class="reference internal" href="#c.PyGILState_Ensure" title="PyGILState_Ensure"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyGILState_Ensure()</span></code></a> must be matched by a call to
<a class="reference internal" href="#c.PyGILState_Release" title="PyGILState_Release"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyGILState_Release()</span></code></a> on the same thread.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyGILState_GetThisThreadState">
<a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><span class="n"><span class="pre">PyThreadState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">PyGILState_GetThisThreadState</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyGILState_GetThisThreadState" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Get the <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a> for this thread. May return <code class="docutils literal notranslate"><span class="pre">NULL</span></code> if no
GILState API has been used on the current thread. Note that the main thread
always has such a thread-state, even if no auto-thread-state call has been
made on the main thread. This is mainly a helper/diagnostic function.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>This function does not account for <a class="reference internal" href="../glossary.html#term-thread-state"><span class="xref std std-term">thread states</span></a> created
by something other than <a class="reference internal" href="#c.PyGILState_Ensure" title="PyGILState_Ensure"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyGILState_Ensure()</span></code></a> (such as <a class="reference internal" href="#c.PyThreadState_New" title="PyThreadState_New"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyThreadState_New()</span></code></a>).
Prefer <a class="reference internal" href="#c.PyThreadState_Get" title="PyThreadState_Get"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyThreadState_Get()</span></code></a> or <a class="reference internal" href="#c.PyThreadState_GetUnchecked" title="PyThreadState_GetUnchecked"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyThreadState_GetUnchecked()</span></code></a>
for most cases.</p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyGILState_Check">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyGILState_Check</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyGILState_Check" title="Link to this definition">¶</a><br /></dt>
<dd><p>Return <code class="docutils literal notranslate"><span class="pre">1</span></code> if the current thread is holding the <a class="reference internal" href="../glossary.html#term-GIL"><span class="xref std std-term">GIL</span></a> and <code class="docutils literal notranslate"><span class="pre">0</span></code> otherwise.
This function can be called from any thread at any time.
Only if it has had its <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">thread state</span></a> initialized
via <a class="reference internal" href="#c.PyGILState_Ensure" title="PyGILState_Ensure"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyGILState_Ensure()</span></code></a> will it return <code class="docutils literal notranslate"><span class="pre">1</span></code>.
This is mainly a helper/diagnostic function. It can be useful
for example in callback contexts or memory allocation functions when
knowing that the <a class="reference internal" href="../glossary.html#term-GIL"><span class="xref std std-term">GIL</span></a> is locked can allow the caller to perform sensitive
actions or otherwise behave differently.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>If the current Python process has ever created a subinterpreter, this
function will <em>always</em> return <code class="docutils literal notranslate"><span class="pre">1</span></code>. Prefer <a class="reference internal" href="#c.PyThreadState_GetUnchecked" title="PyThreadState_GetUnchecked"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyThreadState_GetUnchecked()</span></code></a>
for most cases.</p>
</div>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.4.</span></p>
</div>
</dd></dl>
<p>The following macros are normally used without a trailing semicolon; look for
example usage in the Python source distribution.</p>
<dl class="c macro">
<dt class="sig sig-object c" id="c.Py_BEGIN_ALLOW_THREADS">
<span class="sig-name descname"><span class="n"><span class="pre">Py_BEGIN_ALLOW_THREADS</span></span></span><a class="headerlink" href="#c.Py_BEGIN_ALLOW_THREADS" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>This macro expands to <code class="docutils literal notranslate"><span class="pre">{</span> <span class="pre">PyThreadState</span> <span class="pre">*_save;</span> <span class="pre">_save</span> <span class="pre">=</span> <span class="pre">PyEval_SaveThread();</span></code>.
Note that it contains an opening brace; it must be matched with a following
<a class="reference internal" href="#c.Py_END_ALLOW_THREADS" title="Py_END_ALLOW_THREADS"><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_END_ALLOW_THREADS</span></code></a> macro. See above for further discussion of this
macro.</p>
</dd></dl>
<dl class="c macro">
<dt class="sig sig-object c" id="c.Py_END_ALLOW_THREADS">
<span class="sig-name descname"><span class="n"><span class="pre">Py_END_ALLOW_THREADS</span></span></span><a class="headerlink" href="#c.Py_END_ALLOW_THREADS" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>This macro expands to <code class="docutils literal notranslate"><span class="pre">PyEval_RestoreThread(_save);</span> <span class="pre">}</span></code>. Note that it contains
a closing brace; it must be matched with an earlier
<a class="reference internal" href="#c.Py_BEGIN_ALLOW_THREADS" title="Py_BEGIN_ALLOW_THREADS"><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_BEGIN_ALLOW_THREADS</span></code></a> macro. See above for further discussion of
this macro.</p>
</dd></dl>
<dl class="c macro">
<dt class="sig sig-object c" id="c.Py_BLOCK_THREADS">
<span class="sig-name descname"><span class="n"><span class="pre">Py_BLOCK_THREADS</span></span></span><a class="headerlink" href="#c.Py_BLOCK_THREADS" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>This macro expands to <code class="docutils literal notranslate"><span class="pre">PyEval_RestoreThread(_save);</span></code>: it is equivalent to
<a class="reference internal" href="#c.Py_END_ALLOW_THREADS" title="Py_END_ALLOW_THREADS"><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_END_ALLOW_THREADS</span></code></a> without the closing brace.</p>
</dd></dl>
<dl class="c macro">
<dt class="sig sig-object c" id="c.Py_UNBLOCK_THREADS">
<span class="sig-name descname"><span class="n"><span class="pre">Py_UNBLOCK_THREADS</span></span></span><a class="headerlink" href="#c.Py_UNBLOCK_THREADS" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>This macro expands to <code class="docutils literal notranslate"><span class="pre">_save</span> <span class="pre">=</span> <span class="pre">PyEval_SaveThread();</span></code>: it is equivalent to
<a class="reference internal" href="#c.Py_BEGIN_ALLOW_THREADS" title="Py_BEGIN_ALLOW_THREADS"><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_BEGIN_ALLOW_THREADS</span></code></a> without the opening brace and variable
declaration.</p>
</dd></dl>
</section>
<section id="low-level-api">
<h3>Low-level API<a class="headerlink" href="#low-level-api" title="Link to this heading">¶</a></h3>
<p>All of the following functions must be called after <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a>.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.7: </span><a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a> now initializes the <a class="reference internal" href="../glossary.html#term-GIL"><span class="xref std std-term">GIL</span></a>
and sets an <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a>.</p>
</div>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyInterpreterState_New">
<a class="reference internal" href="#c.PyInterpreterState" title="PyInterpreterState"><span class="n"><span class="pre">PyInterpreterState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">PyInterpreterState_New</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyInterpreterState_New" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Create a new interpreter state object. An <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a> is not needed,
but may optionally exist if it is necessary to serialize calls to this
function.</p>
<p class="audit-hook">Raises an <a class="reference internal" href="../library/sys.html#auditing"><span class="std std-ref">auditing event</span></a> <code class="docutils literal notranslate"><span class="pre">cpython.PyInterpreterState_New</span></code> with no arguments.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyInterpreterState_Clear">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyInterpreterState_Clear</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.PyInterpreterState" title="PyInterpreterState"><span class="n"><span class="pre">PyInterpreterState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">interp</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyInterpreterState_Clear" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Reset all information in an interpreter state object. There must be
an <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a> for the interpreter.</p>
<p class="audit-hook">Raises an <a class="reference internal" href="../library/sys.html#auditing"><span class="std std-ref">auditing event</span></a> <code class="docutils literal notranslate"><span class="pre">cpython.PyInterpreterState_Clear</span></code> with no arguments.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyInterpreterState_Delete">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyInterpreterState_Delete</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.PyInterpreterState" title="PyInterpreterState"><span class="n"><span class="pre">PyInterpreterState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">interp</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyInterpreterState_Delete" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Destroy an interpreter state object. There <strong>should not</strong> be an
<a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a> for the target interpreter. The interpreter
state must have been reset with a previous call to <a class="reference internal" href="#c.PyInterpreterState_Clear" title="PyInterpreterState_Clear"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyInterpreterState_Clear()</span></code></a>.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyThreadState_New">
<a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><span class="n"><span class="pre">PyThreadState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">PyThreadState_New</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.PyInterpreterState" title="PyInterpreterState"><span class="n"><span class="pre">PyInterpreterState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">interp</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyThreadState_New" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Create a new thread state object belonging to the given interpreter object.
An <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a> is not needed.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyThreadState_Clear">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyThreadState_Clear</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><span class="n"><span class="pre">PyThreadState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">tstate</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyThreadState_Clear" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Reset all information in a <a class="reference internal" href="../glossary.html#term-thread-state"><span class="xref std std-term">thread state</span></a> object. <em>tstate</em>
must be <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached</span></a></p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.9: </span>This function now calls the <code class="xref c c-member docutils literal notranslate"><span class="pre">PyThreadState.on_delete</span></code> callback.
Previously, that happened in <a class="reference internal" href="#c.PyThreadState_Delete" title="PyThreadState_Delete"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyThreadState_Delete()</span></code></a>.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.13: </span>The <code class="xref c c-member docutils literal notranslate"><span class="pre">PyThreadState.on_delete</span></code> callback was removed.</p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyThreadState_Delete">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyThreadState_Delete</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><span class="n"><span class="pre">PyThreadState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">tstate</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyThreadState_Delete" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Destroy a <a class="reference internal" href="../glossary.html#term-thread-state"><span class="xref std std-term">thread state</span></a> object. <em>tstate</em> should not
be <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached</span></a> to any thread.
<em>tstate</em> must have been reset with a previous call to
<a class="reference internal" href="#c.PyThreadState_Clear" title="PyThreadState_Clear"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyThreadState_Clear()</span></code></a>.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyThreadState_DeleteCurrent">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyThreadState_DeleteCurrent</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">void</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyThreadState_DeleteCurrent" title="Link to this definition">¶</a><br /></dt>
<dd><p>Detach the <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a> (which must have been reset
with a previous call to <a class="reference internal" href="#c.PyThreadState_Clear" title="PyThreadState_Clear"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyThreadState_Clear()</span></code></a>) and then destroy it.</p>
<p>No <a class="reference internal" href="../glossary.html#term-thread-state"><span class="xref std std-term">thread state</span></a> will be <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached</span></a> upon
returning.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyThreadState_GetFrame">
<a class="reference internal" href="frame.html#c.PyFrameObject" title="PyFrameObject"><span class="n"><span class="pre">PyFrameObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">PyThreadState_GetFrame</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><span class="n"><span class="pre">PyThreadState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">tstate</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyThreadState_GetFrame" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.10.</em><p>Get the current frame of the Python thread state <em>tstate</em>.</p>
<p>Return a <a class="reference internal" href="../glossary.html#term-strong-reference"><span class="xref std std-term">strong reference</span></a>. Return <code class="docutils literal notranslate"><span class="pre">NULL</span></code> if no frame is currently
executing.</p>
<p>See also <a class="reference internal" href="reflection.html#c.PyEval_GetFrame" title="PyEval_GetFrame"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyEval_GetFrame()</span></code></a>.</p>
<p><em>tstate</em> must not be <code class="docutils literal notranslate"><span class="pre">NULL</span></code>, and must be <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached</span></a>.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.9.</span></p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyThreadState_GetID">
<span class="n"><span class="pre">uint64_t</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyThreadState_GetID</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><span class="n"><span class="pre">PyThreadState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">tstate</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyThreadState_GetID" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.10.</em><p>Get the unique <a class="reference internal" href="../glossary.html#term-thread-state"><span class="xref std std-term">thread state</span></a> identifier of the Python thread state <em>tstate</em>.</p>
<p><em>tstate</em> must not be <code class="docutils literal notranslate"><span class="pre">NULL</span></code>, and must be <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached</span></a>.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.9.</span></p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyThreadState_GetInterpreter">
<a class="reference internal" href="#c.PyInterpreterState" title="PyInterpreterState"><span class="n"><span class="pre">PyInterpreterState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">PyThreadState_GetInterpreter</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><span class="n"><span class="pre">PyThreadState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">tstate</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyThreadState_GetInterpreter" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.10.</em><p>Get the interpreter of the Python thread state <em>tstate</em>.</p>
<p><em>tstate</em> must not be <code class="docutils literal notranslate"><span class="pre">NULL</span></code>, and must be <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached</span></a>.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.9.</span></p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyThreadState_EnterTracing">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyThreadState_EnterTracing</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><span class="n"><span class="pre">PyThreadState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">tstate</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyThreadState_EnterTracing" title="Link to this definition">¶</a><br /></dt>
<dd><p>Suspend tracing and profiling in the Python thread state <em>tstate</em>.</p>
<p>Resume them using the <a class="reference internal" href="#c.PyThreadState_LeaveTracing" title="PyThreadState_LeaveTracing"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyThreadState_LeaveTracing()</span></code></a> function.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.11.</span></p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyThreadState_LeaveTracing">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyThreadState_LeaveTracing</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><span class="n"><span class="pre">PyThreadState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">tstate</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyThreadState_LeaveTracing" title="Link to this definition">¶</a><br /></dt>
<dd><p>Resume tracing and profiling in the Python thread state <em>tstate</em> suspended
by the <a class="reference internal" href="#c.PyThreadState_EnterTracing" title="PyThreadState_EnterTracing"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyThreadState_EnterTracing()</span></code></a> function.</p>
<p>See also <a class="reference internal" href="#c.PyEval_SetTrace" title="PyEval_SetTrace"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyEval_SetTrace()</span></code></a> and <a class="reference internal" href="#c.PyEval_SetProfile" title="PyEval_SetProfile"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyEval_SetProfile()</span></code></a>
functions.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.11.</span></p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyInterpreterState_Get">
<a class="reference internal" href="#c.PyInterpreterState" title="PyInterpreterState"><span class="n"><span class="pre">PyInterpreterState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">PyInterpreterState_Get</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">void</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyInterpreterState_Get" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.9.</em><p>Get the current interpreter.</p>
<p>Issue a fatal error if there no <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a>.
It cannot return NULL.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.9.</span></p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyInterpreterState_GetID">
<span class="n"><span class="pre">int64_t</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyInterpreterState_GetID</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.PyInterpreterState" title="PyInterpreterState"><span class="n"><span class="pre">PyInterpreterState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">interp</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyInterpreterState_GetID" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.7.</em><p>Return the interpreter’s unique ID. If there was any error in doing
so then <code class="docutils literal notranslate"><span class="pre">-1</span></code> is returned and an error is set.</p>
<p>The caller must have an <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a>.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.7.</span></p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyInterpreterState_GetDict">
<a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">PyInterpreterState_GetDict</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.PyInterpreterState" title="PyInterpreterState"><span class="n"><span class="pre">PyInterpreterState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">interp</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyInterpreterState_GetDict" title="Link to this definition">¶</a><br /></dt>
<dd><em class="refcount return_borrowed_ref">Return value: Borrowed reference.</em><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.8.</em><p>Return a dictionary in which interpreter-specific data may be stored.
If this function returns <code class="docutils literal notranslate"><span class="pre">NULL</span></code> then no exception has been raised and
the caller should assume no interpreter-specific dict is available.</p>
<p>This is not a replacement for <a class="reference internal" href="module.html#c.PyModule_GetState" title="PyModule_GetState"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyModule_GetState()</span></code></a>, which
extensions should use to store interpreter-specific state information.</p>
<p>The returned dictionary is borrowed from the interpreter and is valid until
interpreter shutdown.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.8.</span></p>
</div>
</dd></dl>
<dl class="c type">
<dt class="sig sig-object c" id="c._PyFrameEvalFunction">
<span class="k"><span class="pre">typedef</span></span><span class="w"> </span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="p"><span class="pre">(</span></span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">_PyFrameEvalFunction</span></span></span><span class="p"><span class="pre">)</span></span><span class="p"><span class="pre">(</span></span><a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><span class="n"><span class="pre">PyThreadState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">tstate</span></span><span class="p"><span class="pre">,</span></span><span class="w"> </span><a class="reference internal" href="frame.html#c._PyInterpreterFrame" title="_PyInterpreterFrame"><span class="n"><span class="pre">_PyInterpreterFrame</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">frame</span></span><span class="p"><span class="pre">,</span></span><span class="w"> </span><span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">throwflag</span></span><span class="p"><span class="pre">)</span></span><a class="headerlink" href="#c._PyFrameEvalFunction" title="Link to this definition">¶</a><br /></dt>
<dd><p>Type of a frame evaluation function.</p>
<p>The <em>throwflag</em> parameter is used by the <code class="docutils literal notranslate"><span class="pre">throw()</span></code> method of generators:
if non-zero, handle the current exception.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.9: </span>The function now takes a <em>tstate</em> parameter.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.11: </span>The <em>frame</em> parameter changed from <code class="docutils literal notranslate"><span class="pre">PyFrameObject*</span></code> to <code class="docutils literal notranslate"><span class="pre">_PyInterpreterFrame*</span></code>.</p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c._PyInterpreterState_GetEvalFrameFunc">
<a class="reference internal" href="#c._PyFrameEvalFunction" title="_PyFrameEvalFunction"><span class="n"><span class="pre">_PyFrameEvalFunction</span></span></a><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">_PyInterpreterState_GetEvalFrameFunc</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.PyInterpreterState" title="PyInterpreterState"><span class="n"><span class="pre">PyInterpreterState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">interp</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c._PyInterpreterState_GetEvalFrameFunc" title="Link to this definition">¶</a><br /></dt>
<dd><p>Get the frame evaluation function.</p>
<p>See the <span class="target" id="index-37"></span><a class="pep reference external" href="https://peps.python.org/pep-0523/"><strong>PEP 523</strong></a> “Adding a frame evaluation API to CPython”.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.9.</span></p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c._PyInterpreterState_SetEvalFrameFunc">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">_PyInterpreterState_SetEvalFrameFunc</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.PyInterpreterState" title="PyInterpreterState"><span class="n"><span class="pre">PyInterpreterState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">interp</span></span>, <a class="reference internal" href="#c._PyFrameEvalFunction" title="_PyFrameEvalFunction"><span class="n"><span class="pre">_PyFrameEvalFunction</span></span></a><span class="w"> </span><span class="n"><span class="pre">eval_frame</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c._PyInterpreterState_SetEvalFrameFunc" title="Link to this definition">¶</a><br /></dt>
<dd><p>Set the frame evaluation function.</p>
<p>See the <span class="target" id="index-38"></span><a class="pep reference external" href="https://peps.python.org/pep-0523/"><strong>PEP 523</strong></a> “Adding a frame evaluation API to CPython”.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.9.</span></p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyThreadState_GetDict">
<a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">PyThreadState_GetDict</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyThreadState_GetDict" title="Link to this definition">¶</a><br /></dt>
<dd><em class="refcount return_borrowed_ref">Return value: Borrowed reference.</em><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Return a dictionary in which extensions can store thread-specific state
information. Each extension should use a unique key to use to store state in
the dictionary. It is okay to call this function when no <a class="reference internal" href="../glossary.html#term-thread-state"><span class="xref std std-term">thread state</span></a>
is <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached</span></a>. If this function returns
<code class="docutils literal notranslate"><span class="pre">NULL</span></code>, no exception has been raised and the caller should assume no
thread state is attached.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyThreadState_SetAsyncExc">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyThreadState_SetAsyncExc</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">unsigned</span></span><span class="w"> </span><span class="kt"><span class="pre">long</span></span><span class="w"> </span><span class="n"><span class="pre">id</span></span>, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">exc</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyThreadState_SetAsyncExc" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Asynchronously raise an exception in a thread. The <em>id</em> argument is the thread
id of the target thread; <em>exc</em> is the exception object to be raised. This
function does not steal any references to <em>exc</em>. To prevent naive misuse, you
must write your own C extension to call this. Must be called with an <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a>.
Returns the number of thread states modified; this is normally one, but will be
zero if the thread id isn’t found. If <em>exc</em> is <code class="docutils literal notranslate"><span class="pre">NULL</span></code>, the pending
exception (if any) for the thread is cleared. This raises no exceptions.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.7: </span>The type of the <em>id</em> parameter changed from <span class="c-expr sig sig-inline c"><span class="kt">long</span></span> to
<span class="c-expr sig sig-inline c"><span class="kt">unsigned</span><span class="w"> </span><span class="kt">long</span></span>.</p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyEval_AcquireThread">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyEval_AcquireThread</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><span class="n"><span class="pre">PyThreadState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">tstate</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyEval_AcquireThread" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p><a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">Attach</span></a> <em>tstate</em> to the current thread,
which must not be <code class="docutils literal notranslate"><span class="pre">NULL</span></code> or already <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached</span></a>.</p>
<p>The calling thread must not already have an <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a>.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>Calling this function from a thread when the runtime is finalizing will
hang the thread until the program exits, even if the thread was not
created by Python. Refer to
<a class="reference internal" href="#cautions-regarding-runtime-finalization"><span class="std std-ref">Cautions regarding runtime finalization</span></a> for more details.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.8: </span>Updated to be consistent with <a class="reference internal" href="#c.PyEval_RestoreThread" title="PyEval_RestoreThread"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyEval_RestoreThread()</span></code></a>,
<a class="reference internal" href="#c.Py_END_ALLOW_THREADS" title="Py_END_ALLOW_THREADS"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_END_ALLOW_THREADS()</span></code></a>, and <a class="reference internal" href="#c.PyGILState_Ensure" title="PyGILState_Ensure"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyGILState_Ensure()</span></code></a>,
and terminate the current thread if called while the interpreter is finalizing.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.14: </span>Hangs the current thread, rather than terminating it, if called while the
interpreter is finalizing.</p>
</div>
<p><a class="reference internal" href="#c.PyEval_RestoreThread" title="PyEval_RestoreThread"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyEval_RestoreThread()</span></code></a> is a higher-level function which is always
available (even when threads have not been initialized).</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyEval_ReleaseThread">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyEval_ReleaseThread</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><span class="n"><span class="pre">PyThreadState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">tstate</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyEval_ReleaseThread" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Detach the <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a>.
The <em>tstate</em> argument, which must not be <code class="docutils literal notranslate"><span class="pre">NULL</span></code>, is only used to check
that it represents the <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a> — if it isn’t, a fatal error is
reported.</p>
<p><a class="reference internal" href="#c.PyEval_SaveThread" title="PyEval_SaveThread"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyEval_SaveThread()</span></code></a> is a higher-level function which is always
available (even when threads have not been initialized).</p>
</dd></dl>
</section>
</section>
<section id="sub-interpreter-support">
<span id="id2"></span><h2>Sub-interpreter support<a class="headerlink" href="#sub-interpreter-support" title="Link to this heading">¶</a></h2>
<p>While in most uses, you will only embed a single Python interpreter, there
are cases where you need to create several independent interpreters in the
same process and perhaps even in the same thread. Sub-interpreters allow
you to do that.</p>
<p>The “main” interpreter is the first one created when the runtime initializes.
It is usually the only Python interpreter in a process. Unlike sub-interpreters,
the main interpreter has unique process-global responsibilities like signal
handling. It is also responsible for execution during runtime initialization and
is usually the active interpreter during runtime finalization. The
<a class="reference internal" href="#c.PyInterpreterState_Main" title="PyInterpreterState_Main"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyInterpreterState_Main()</span></code></a> function returns a pointer to its state.</p>
<p>You can switch between sub-interpreters using the <a class="reference internal" href="#c.PyThreadState_Swap" title="PyThreadState_Swap"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyThreadState_Swap()</span></code></a>
function. You can create and destroy them using the following functions:</p>
<dl class="c type">
<dt class="sig sig-object c" id="c.PyInterpreterConfig">
<span class="k"><span class="pre">type</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyInterpreterConfig</span></span></span><a class="headerlink" href="#c.PyInterpreterConfig" title="Link to this definition">¶</a><br /></dt>
<dd><p>Structure containing most parameters to configure a sub-interpreter.
Its values are used only in <a class="reference internal" href="#c.Py_NewInterpreterFromConfig" title="Py_NewInterpreterFromConfig"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_NewInterpreterFromConfig()</span></code></a> and
never modified by the runtime.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.12.</span></p>
</div>
<p>Structure fields:</p>
<dl class="c member">
<dt class="sig sig-object c" id="c.PyInterpreterConfig.use_main_obmalloc">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">use_main_obmalloc</span></span></span><a class="headerlink" href="#c.PyInterpreterConfig.use_main_obmalloc" title="Link to this definition">¶</a><br /></dt>
<dd><p>If this is <code class="docutils literal notranslate"><span class="pre">0</span></code> then the sub-interpreter will use its own
“object” allocator state.
Otherwise it will use (share) the main interpreter’s.</p>
<p>If this is <code class="docutils literal notranslate"><span class="pre">0</span></code> then
<a class="reference internal" href="#c.PyInterpreterConfig.check_multi_interp_extensions" title="PyInterpreterConfig.check_multi_interp_extensions"><code class="xref c c-member docutils literal notranslate"><span class="pre">check_multi_interp_extensions</span></code></a>
must be <code class="docutils literal notranslate"><span class="pre">1</span></code> (non-zero).
If this is <code class="docutils literal notranslate"><span class="pre">1</span></code> then <a class="reference internal" href="#c.PyInterpreterConfig.gil" title="PyInterpreterConfig.gil"><code class="xref c c-member docutils literal notranslate"><span class="pre">gil</span></code></a>
must not be <a class="reference internal" href="#c.PyInterpreterConfig_OWN_GIL" title="PyInterpreterConfig_OWN_GIL"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyInterpreterConfig_OWN_GIL</span></code></a>.</p>
</dd></dl>
<dl class="c member">
<dt class="sig sig-object c" id="c.PyInterpreterConfig.allow_fork">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">allow_fork</span></span></span><a class="headerlink" href="#c.PyInterpreterConfig.allow_fork" title="Link to this definition">¶</a><br /></dt>
<dd><p>If this is <code class="docutils literal notranslate"><span class="pre">0</span></code> then the runtime will not support forking the
process in any thread where the sub-interpreter is currently active.
Otherwise fork is unrestricted.</p>
<p>Note that the <a class="reference internal" href="../library/subprocess.html#module-subprocess" title="subprocess: Subprocess management."><code class="xref py py-mod docutils literal notranslate"><span class="pre">subprocess</span></code></a> module still works
when fork is disallowed.</p>
</dd></dl>
<dl class="c member">
<dt class="sig sig-object c" id="c.PyInterpreterConfig.allow_exec">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">allow_exec</span></span></span><a class="headerlink" href="#c.PyInterpreterConfig.allow_exec" title="Link to this definition">¶</a><br /></dt>
<dd><p>If this is <code class="docutils literal notranslate"><span class="pre">0</span></code> then the runtime will not support replacing the
current process via exec (e.g. <a class="reference internal" href="../library/os.html#os.execv" title="os.execv"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.execv()</span></code></a>) in any thread
where the sub-interpreter is currently active.
Otherwise exec is unrestricted.</p>
<p>Note that the <a class="reference internal" href="../library/subprocess.html#module-subprocess" title="subprocess: Subprocess management."><code class="xref py py-mod docutils literal notranslate"><span class="pre">subprocess</span></code></a> module still works
when exec is disallowed.</p>
</dd></dl>
<dl class="c member">
<dt class="sig sig-object c" id="c.PyInterpreterConfig.allow_threads">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">allow_threads</span></span></span><a class="headerlink" href="#c.PyInterpreterConfig.allow_threads" title="Link to this definition">¶</a><br /></dt>
<dd><p>If this is <code class="docutils literal notranslate"><span class="pre">0</span></code> then the sub-interpreter’s <a class="reference internal" href="../library/threading.html#module-threading" title="threading: Thread-based parallelism."><code class="xref py py-mod docutils literal notranslate"><span class="pre">threading</span></code></a> module
won’t create threads.
Otherwise threads are allowed.</p>
</dd></dl>
<dl class="c member">
<dt class="sig sig-object c" id="c.PyInterpreterConfig.allow_daemon_threads">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">allow_daemon_threads</span></span></span><a class="headerlink" href="#c.PyInterpreterConfig.allow_daemon_threads" title="Link to this definition">¶</a><br /></dt>
<dd><p>If this is <code class="docutils literal notranslate"><span class="pre">0</span></code> then the sub-interpreter’s <a class="reference internal" href="../library/threading.html#module-threading" title="threading: Thread-based parallelism."><code class="xref py py-mod docutils literal notranslate"><span class="pre">threading</span></code></a> module
won’t create daemon threads.
Otherwise daemon threads are allowed (as long as
<a class="reference internal" href="#c.PyInterpreterConfig.allow_threads" title="PyInterpreterConfig.allow_threads"><code class="xref c c-member docutils literal notranslate"><span class="pre">allow_threads</span></code></a> is non-zero).</p>
</dd></dl>
<dl class="c member">
<dt class="sig sig-object c" id="c.PyInterpreterConfig.check_multi_interp_extensions">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">check_multi_interp_extensions</span></span></span><a class="headerlink" href="#c.PyInterpreterConfig.check_multi_interp_extensions" title="Link to this definition">¶</a><br /></dt>
<dd><p>If this is <code class="docutils literal notranslate"><span class="pre">0</span></code> then all extension modules may be imported,
including legacy (single-phase init) modules,
in any thread where the sub-interpreter is currently active.
Otherwise only multi-phase init extension modules
(see <span class="target" id="index-39"></span><a class="pep reference external" href="https://peps.python.org/pep-0489/"><strong>PEP 489</strong></a>) may be imported.
(Also see <a class="reference internal" href="module.html#c.Py_mod_multiple_interpreters" title="Py_mod_multiple_interpreters"><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_mod_multiple_interpreters</span></code></a>.)</p>
<p>This must be <code class="docutils literal notranslate"><span class="pre">1</span></code> (non-zero) if
<a class="reference internal" href="#c.PyInterpreterConfig.use_main_obmalloc" title="PyInterpreterConfig.use_main_obmalloc"><code class="xref c c-member docutils literal notranslate"><span class="pre">use_main_obmalloc</span></code></a> is <code class="docutils literal notranslate"><span class="pre">0</span></code>.</p>
</dd></dl>
<dl class="c member">
<dt class="sig sig-object c" id="c.PyInterpreterConfig.gil">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">gil</span></span></span><a class="headerlink" href="#c.PyInterpreterConfig.gil" title="Link to this definition">¶</a><br /></dt>
<dd><p>This determines the operation of the GIL for the sub-interpreter.
It may be one of the following:</p>
<dl class="c macro">
<dt class="sig sig-object c" id="c.PyInterpreterConfig_DEFAULT_GIL">
<span class="sig-name descname"><span class="n"><span class="pre">PyInterpreterConfig_DEFAULT_GIL</span></span></span><a class="headerlink" href="#c.PyInterpreterConfig_DEFAULT_GIL" title="Link to this definition">¶</a><br /></dt>
<dd><p>Use the default selection (<a class="reference internal" href="#c.PyInterpreterConfig_SHARED_GIL" title="PyInterpreterConfig_SHARED_GIL"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyInterpreterConfig_SHARED_GIL</span></code></a>).</p>
</dd></dl>
<dl class="c macro">
<dt class="sig sig-object c" id="c.PyInterpreterConfig_SHARED_GIL">
<span class="sig-name descname"><span class="n"><span class="pre">PyInterpreterConfig_SHARED_GIL</span></span></span><a class="headerlink" href="#c.PyInterpreterConfig_SHARED_GIL" title="Link to this definition">¶</a><br /></dt>
<dd><p>Use (share) the main interpreter’s GIL.</p>
</dd></dl>
<dl class="c macro">
<dt class="sig sig-object c" id="c.PyInterpreterConfig_OWN_GIL">
<span class="sig-name descname"><span class="n"><span class="pre">PyInterpreterConfig_OWN_GIL</span></span></span><a class="headerlink" href="#c.PyInterpreterConfig_OWN_GIL" title="Link to this definition">¶</a><br /></dt>
<dd><p>Use the sub-interpreter’s own GIL.</p>
</dd></dl>
<p>If this is <a class="reference internal" href="#c.PyInterpreterConfig_OWN_GIL" title="PyInterpreterConfig_OWN_GIL"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyInterpreterConfig_OWN_GIL</span></code></a> then
<a class="reference internal" href="#c.PyInterpreterConfig.use_main_obmalloc" title="PyInterpreterConfig.use_main_obmalloc"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyInterpreterConfig.use_main_obmalloc</span></code></a> must be <code class="docutils literal notranslate"><span class="pre">0</span></code>.</p>
</dd></dl>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_NewInterpreterFromConfig">
<a class="reference internal" href="init_config.html#c.PyStatus" title="PyStatus"><span class="n"><span class="pre">PyStatus</span></span></a><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_NewInterpreterFromConfig</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><span class="n"><span class="pre">PyThreadState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">tstate_p</span></span>, <span class="k"><span class="pre">const</span></span><span class="w"> </span><a class="reference internal" href="#c.PyInterpreterConfig" title="PyInterpreterConfig"><span class="n"><span class="pre">PyInterpreterConfig</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">config</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_NewInterpreterFromConfig" title="Link to this definition">¶</a><br /></dt>
<dd><p id="index-40">Create a new sub-interpreter. This is an (almost) totally separate environment
for the execution of Python code. In particular, the new interpreter has
separate, independent versions of all imported modules, including the
fundamental modules <a class="reference internal" href="../library/builtins.html#module-builtins" title="builtins: The module that provides the built-in namespace."><code class="xref py py-mod docutils literal notranslate"><span class="pre">builtins</span></code></a>, <a class="reference internal" href="../library/__main__.html#module-__main__" title="__main__: The environment where top-level code is run. Covers command-line interfaces, import-time behavior, and ``__name__ == '__main__'``."><code class="xref py py-mod docutils literal notranslate"><span class="pre">__main__</span></code></a> and <a class="reference internal" href="../library/sys.html#module-sys" title="sys: Access system-specific parameters and functions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">sys</span></code></a>. The
table of loaded modules (<code class="docutils literal notranslate"><span class="pre">sys.modules</span></code>) and the module search path
(<code class="docutils literal notranslate"><span class="pre">sys.path</span></code>) are also separate. The new environment has no <code class="docutils literal notranslate"><span class="pre">sys.argv</span></code>
variable. It has new standard I/O stream file objects <code class="docutils literal notranslate"><span class="pre">sys.stdin</span></code>,
<code class="docutils literal notranslate"><span class="pre">sys.stdout</span></code> and <code class="docutils literal notranslate"><span class="pre">sys.stderr</span></code> (however these refer to the same underlying
file descriptors).</p>
<p>The given <em>config</em> controls the options with which the interpreter
is initialized.</p>
<p>Upon success, <em>tstate_p</em> will be set to the first <a class="reference internal" href="../glossary.html#term-thread-state"><span class="xref std std-term">thread state</span></a>
created in the new sub-interpreter. This thread state is
<a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached</span></a>.
Note that no actual thread is created; see the discussion of thread states
below. If creation of the new interpreter is unsuccessful,
<em>tstate_p</em> is set to <code class="docutils literal notranslate"><span class="pre">NULL</span></code>;
no exception is set since the exception state is stored in the
<a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a>, which might not exist.</p>
<p>Like all other Python/C API functions, an <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a>
must be present before calling this function, but it might be detached upon
returning. On success, the returned thread state will be <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached</span></a>.
If the sub-interpreter is created with its own <a class="reference internal" href="../glossary.html#term-GIL"><span class="xref std std-term">GIL</span></a> then the
<a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a> of the calling interpreter will be detached.
When the function returns, the new interpreter’s <a class="reference internal" href="../glossary.html#term-thread-state"><span class="xref std std-term">thread state</span></a>
will be <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached</span></a> to the current thread and
the previous interpreter’s <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a> will remain detached.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.12.</span></p>
</div>
<p>Sub-interpreters are most effective when isolated from each other,
with certain functionality restricted:</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="n">PyInterpreterConfig</span><span class="w"> </span><span class="n">config</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="p">.</span><span class="n">use_main_obmalloc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span>
<span class="w"> </span><span class="p">.</span><span class="n">allow_fork</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span>
<span class="w"> </span><span class="p">.</span><span class="n">allow_exec</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span>
<span class="w"> </span><span class="p">.</span><span class="n">allow_threads</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span>
<span class="w"> </span><span class="p">.</span><span class="n">allow_daemon_threads</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span>
<span class="w"> </span><span class="p">.</span><span class="n">check_multi_interp_extensions</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span>
<span class="w"> </span><span class="p">.</span><span class="n">gil</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">PyInterpreterConfig_OWN_GIL</span><span class="p">,</span>
<span class="p">};</span>
<span class="n">PyThreadState</span><span class="w"> </span><span class="o">*</span><span class="n">tstate</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">NULL</span><span class="p">;</span>
<span class="n">PyStatus</span><span class="w"> </span><span class="n">status</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Py_NewInterpreterFromConfig</span><span class="p">(</span><span class="o">&</span><span class="n">tstate</span><span class="p">,</span><span class="w"> </span><span class="o">&</span><span class="n">config</span><span class="p">);</span>
<span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">PyStatus_Exception</span><span class="p">(</span><span class="n">status</span><span class="p">))</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">Py_ExitStatusException</span><span class="p">(</span><span class="n">status</span><span class="p">);</span>
<span class="p">}</span>
</pre></div>
</div>
<p>Note that the config is used only briefly and does not get modified.
During initialization the config’s values are converted into various
<a class="reference internal" href="#c.PyInterpreterState" title="PyInterpreterState"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyInterpreterState</span></code></a> values. A read-only copy of the config
may be stored internally on the <a class="reference internal" href="#c.PyInterpreterState" title="PyInterpreterState"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyInterpreterState</span></code></a>.</p>
<p id="index-41">Extension modules are shared between (sub-)interpreters as follows:</p>
<ul>
<li><p>For modules using multi-phase initialization,
e.g. <a class="reference internal" href="module.html#c.PyModule_FromDefAndSpec" title="PyModule_FromDefAndSpec"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyModule_FromDefAndSpec()</span></code></a>, a separate module object is
created and initialized for each interpreter.
Only C-level static and global variables are shared between these
module objects.</p></li>
<li><p>For modules using single-phase initialization,
e.g. <a class="reference internal" href="module.html#c.PyModule_Create" title="PyModule_Create"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyModule_Create()</span></code></a>, the first time a particular extension
is imported, it is initialized normally, and a (shallow) copy of its
module’s dictionary is squirreled away.
When the same extension is imported by another (sub-)interpreter, a new
module is initialized and filled with the contents of this copy; the
extension’s <code class="docutils literal notranslate"><span class="pre">init</span></code> function is not called.
Objects in the module’s dictionary thus end up shared across
(sub-)interpreters, which might cause unwanted behavior (see
<a class="reference internal" href="#bugs-and-caveats">Bugs and caveats</a> below).</p>
<p>Note that this is different from what happens when an extension is
imported after the interpreter has been completely re-initialized by
calling <a class="reference internal" href="#c.Py_FinalizeEx" title="Py_FinalizeEx"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_FinalizeEx()</span></code></a> and <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Initialize()</span></code></a>; in that
case, the extension’s <code class="docutils literal notranslate"><span class="pre">initmodule</span></code> function <em>is</em> called again.
As with multi-phase initialization, this means that only C-level static
and global variables are shared between these modules.</p>
</li>
</ul>
<span class="target" id="index-42"></span></dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_NewInterpreter">
<a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><span class="n"><span class="pre">PyThreadState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">Py_NewInterpreter</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">void</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_NewInterpreter" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p id="index-43">Create a new sub-interpreter. This is essentially just a wrapper
around <a class="reference internal" href="#c.Py_NewInterpreterFromConfig" title="Py_NewInterpreterFromConfig"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_NewInterpreterFromConfig()</span></code></a> with a config that
preserves the existing behavior. The result is an unisolated
sub-interpreter that shares the main interpreter’s GIL, allows
fork/exec, allows daemon threads, and allows single-phase init
modules.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_EndInterpreter">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_EndInterpreter</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><span class="n"><span class="pre">PyThreadState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">tstate</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_EndInterpreter" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p id="index-44">Destroy the (sub-)interpreter represented by the given <a class="reference internal" href="../glossary.html#term-thread-state"><span class="xref std std-term">thread state</span></a>.
The given thread state must be <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached</span></a>.
When the call returns, there will be no <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a>.
All thread states associated with this interpreter are destroyed.</p>
<p><a class="reference internal" href="#c.Py_FinalizeEx" title="Py_FinalizeEx"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_FinalizeEx()</span></code></a> will destroy all sub-interpreters that
haven’t been explicitly destroyed at that point.</p>
</dd></dl>
<section id="a-per-interpreter-gil">
<span id="per-interpreter-gil"></span><h3>A Per-Interpreter GIL<a class="headerlink" href="#a-per-interpreter-gil" title="Link to this heading">¶</a></h3>
<p>Using <a class="reference internal" href="#c.Py_NewInterpreterFromConfig" title="Py_NewInterpreterFromConfig"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_NewInterpreterFromConfig()</span></code></a> you can create
a sub-interpreter that is completely isolated from other interpreters,
including having its own GIL. The most important benefit of this
isolation is that such an interpreter can execute Python code without
being blocked by other interpreters or blocking any others. Thus a
single Python process can truly take advantage of multiple CPU cores
when running Python code. The isolation also encourages a different
approach to concurrency than that of just using threads.
(See <span class="target" id="index-45"></span><a class="pep reference external" href="https://peps.python.org/pep-0554/"><strong>PEP 554</strong></a> and <span class="target" id="index-46"></span><a class="pep reference external" href="https://peps.python.org/pep-0684/"><strong>PEP 684</strong></a>.)</p>
<p>Using an isolated interpreter requires vigilance in preserving that
isolation. That especially means not sharing any objects or mutable
state without guarantees about thread-safety. Even objects that are
otherwise immutable (e.g. <code class="docutils literal notranslate"><span class="pre">None</span></code>, <code class="docutils literal notranslate"><span class="pre">(1,</span> <span class="pre">5)</span></code>) can’t normally be shared
because of the refcount. One simple but less-efficient approach around
this is to use a global lock around all use of some state (or object).
Alternately, effectively immutable objects (like integers or strings)
can be made safe in spite of their refcounts by making them <a class="reference internal" href="../glossary.html#term-immortal"><span class="xref std std-term">immortal</span></a>.
In fact, this has been done for the builtin singletons, small integers,
and a number of other builtin objects.</p>
<p>If you preserve isolation then you will have access to proper multi-core
computing without the complications that come with free-threading.
Failure to preserve isolation will expose you to the full consequences
of free-threading, including races and hard-to-debug crashes.</p>
<p>Aside from that, one of the main challenges of using multiple isolated
interpreters is how to communicate between them safely (not break
isolation) and efficiently. The runtime and stdlib do not provide
any standard approach to this yet. A future stdlib module would help
mitigate the effort of preserving isolation and expose effective tools
for communicating (and sharing) data between interpreters.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.12.</span></p>
</div>
</section>
<section id="bugs-and-caveats">
<h3>Bugs and caveats<a class="headerlink" href="#bugs-and-caveats" title="Link to this heading">¶</a></h3>
<p>Because sub-interpreters (and the main interpreter) are part of the same
process, the insulation between them isn’t perfect — for example, using
low-level file operations like <a class="reference internal" href="../library/os.html#os.close" title="os.close"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.close()</span></code></a> they can
(accidentally or maliciously) affect each other’s open files. Because of the
way extensions are shared between (sub-)interpreters, some extensions may not
work properly; this is especially likely when using single-phase initialization
or (static) global variables.
It is possible to insert objects created in one sub-interpreter into
a namespace of another (sub-)interpreter; this should be avoided if possible.</p>
<p>Special care should be taken to avoid sharing user-defined functions,
methods, instances or classes between sub-interpreters, since import
operations executed by such objects may affect the wrong (sub-)interpreter’s
dictionary of loaded modules. It is equally important to avoid sharing
objects from which the above are reachable.</p>
<p>Also note that combining this functionality with <code class="docutils literal notranslate"><span class="pre">PyGILState_*</span></code> APIs
is delicate, because these APIs assume a bijection between Python thread states
and OS-level threads, an assumption broken by the presence of sub-interpreters.
It is highly recommended that you don’t switch sub-interpreters between a pair
of matching <a class="reference internal" href="#c.PyGILState_Ensure" title="PyGILState_Ensure"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyGILState_Ensure()</span></code></a> and <a class="reference internal" href="#c.PyGILState_Release" title="PyGILState_Release"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyGILState_Release()</span></code></a> calls.
Furthermore, extensions (such as <a class="reference internal" href="../library/ctypes.html#module-ctypes" title="ctypes: A foreign function library for Python."><code class="xref py py-mod docutils literal notranslate"><span class="pre">ctypes</span></code></a>) using these APIs to allow calling
of Python code from non-Python created threads will probably be broken when using
sub-interpreters.</p>
</section>
</section>
<section id="asynchronous-notifications">
<h2>Asynchronous Notifications<a class="headerlink" href="#asynchronous-notifications" title="Link to this heading">¶</a></h2>
<p>A mechanism is provided to make asynchronous notifications to the main
interpreter thread. These notifications take the form of a function
pointer and a void pointer argument.</p>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_AddPendingCall">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_AddPendingCall</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="p"><span class="pre">(</span></span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">func</span></span><span class="p"><span class="pre">)</span></span><span class="p"><span class="pre">(</span></span><span class="kt"><span class="pre">void</span></span><span class="p"><span class="pre">*</span></span><span class="p"><span class="pre">)</span></span>, <span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">arg</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_AddPendingCall" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Schedule a function to be called from the main interpreter thread. On
success, <code class="docutils literal notranslate"><span class="pre">0</span></code> is returned and <em>func</em> is queued for being called in the
main thread. On failure, <code class="docutils literal notranslate"><span class="pre">-1</span></code> is returned without setting any exception.</p>
<p>When successfully queued, <em>func</em> will be <em>eventually</em> called from the
main interpreter thread with the argument <em>arg</em>. It will be called
asynchronously with respect to normally running Python code, but with
both these conditions met:</p>
<ul class="simple">
<li><p>on a <a class="reference internal" href="../glossary.html#term-bytecode"><span class="xref std std-term">bytecode</span></a> boundary;</p></li>
<li><p>with the main thread holding an <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a>
(<em>func</em> can therefore use the full C API).</p></li>
</ul>
<p><em>func</em> must return <code class="docutils literal notranslate"><span class="pre">0</span></code> on success, or <code class="docutils literal notranslate"><span class="pre">-1</span></code> on failure with an exception
set. <em>func</em> won’t be interrupted to perform another asynchronous
notification recursively, but it can still be interrupted to switch
threads if the <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">thread state</span></a> is detached.</p>
<p>This function doesn’t need an <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a>. However, to call this
function in a subinterpreter, the caller must have an <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a>.
Otherwise, the function <em>func</em> can be scheduled to be called from the wrong interpreter.</p>
<div class="admonition warning">
<p class="admonition-title">Warning</p>
<p>This is a low-level function, only useful for very special cases.
There is no guarantee that <em>func</em> will be called as quick as
possible. If the main thread is busy executing a system call,
<em>func</em> won’t be called before the system call returns. This
function is generally <strong>not</strong> suitable for calling Python code from
arbitrary C threads. Instead, use the <a class="reference internal" href="#gilstate"><span class="std std-ref">PyGILState API</span></a>.</p>
</div>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.1.</span></p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.9: </span>If this function is called in a subinterpreter, the function <em>func</em> is
now scheduled to be called from the subinterpreter, rather than being
called from the main interpreter. Each subinterpreter now has its own
list of scheduled calls.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.12: </span>This function now always schedules <em>func</em> to be run in the main
interpreter.</p>
</div>
</dd></dl>
</section>
<section id="profiling-and-tracing">
<span id="profiling"></span><h2>Profiling and Tracing<a class="headerlink" href="#profiling-and-tracing" title="Link to this heading">¶</a></h2>
<p>The Python interpreter provides some low-level support for attaching profiling
and execution tracing facilities. These are used for profiling, debugging, and
coverage analysis tools.</p>
<p>This C interface allows the profiling or tracing code to avoid the overhead of
calling through Python-level callable objects, making a direct C function call
instead. The essential attributes of the facility have not changed; the
interface allows trace functions to be installed per-thread, and the basic
events reported to the trace function are the same as had been reported to the
Python-level trace functions in previous versions.</p>
<dl class="c type">
<dt class="sig sig-object c" id="c.Py_tracefunc">
<span class="k"><span class="pre">typedef</span></span><span class="w"> </span><span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="p"><span class="pre">(</span></span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">Py_tracefunc</span></span></span><span class="p"><span class="pre">)</span></span><span class="p"><span class="pre">(</span></span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">obj</span></span><span class="p"><span class="pre">,</span></span><span class="w"> </span><a class="reference internal" href="frame.html#c.PyFrameObject" title="PyFrameObject"><span class="n"><span class="pre">PyFrameObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">frame</span></span><span class="p"><span class="pre">,</span></span><span class="w"> </span><span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">what</span></span><span class="p"><span class="pre">,</span></span><span class="w"> </span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">arg</span></span><span class="p"><span class="pre">)</span></span><a class="headerlink" href="#c.Py_tracefunc" title="Link to this definition">¶</a><br /></dt>
<dd><p>The type of the trace function registered using <a class="reference internal" href="#c.PyEval_SetProfile" title="PyEval_SetProfile"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyEval_SetProfile()</span></code></a> and
<a class="reference internal" href="#c.PyEval_SetTrace" title="PyEval_SetTrace"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyEval_SetTrace()</span></code></a>. The first parameter is the object passed to the
registration function as <em>obj</em>, <em>frame</em> is the frame object to which the event
pertains, <em>what</em> is one of the constants <a class="reference internal" href="#c.PyTrace_CALL" title="PyTrace_CALL"><code class="xref c c-data docutils literal notranslate"><span class="pre">PyTrace_CALL</span></code></a>,
<a class="reference internal" href="#c.PyTrace_EXCEPTION" title="PyTrace_EXCEPTION"><code class="xref c c-data docutils literal notranslate"><span class="pre">PyTrace_EXCEPTION</span></code></a>, <a class="reference internal" href="#c.PyTrace_LINE" title="PyTrace_LINE"><code class="xref c c-data docutils literal notranslate"><span class="pre">PyTrace_LINE</span></code></a>, <a class="reference internal" href="#c.PyTrace_RETURN" title="PyTrace_RETURN"><code class="xref c c-data docutils literal notranslate"><span class="pre">PyTrace_RETURN</span></code></a>,
<a class="reference internal" href="#c.PyTrace_C_CALL" title="PyTrace_C_CALL"><code class="xref c c-data docutils literal notranslate"><span class="pre">PyTrace_C_CALL</span></code></a>, <a class="reference internal" href="#c.PyTrace_C_EXCEPTION" title="PyTrace_C_EXCEPTION"><code class="xref c c-data docutils literal notranslate"><span class="pre">PyTrace_C_EXCEPTION</span></code></a>, <a class="reference internal" href="#c.PyTrace_C_RETURN" title="PyTrace_C_RETURN"><code class="xref c c-data docutils literal notranslate"><span class="pre">PyTrace_C_RETURN</span></code></a>,
or <a class="reference internal" href="#c.PyTrace_OPCODE" title="PyTrace_OPCODE"><code class="xref c c-data docutils literal notranslate"><span class="pre">PyTrace_OPCODE</span></code></a>, and <em>arg</em> depends on the value of <em>what</em>:</p>
<table class="docutils align-default">
<thead>
<tr class="row-odd"><th class="head"><p>Value of <em>what</em></p></th>
<th class="head"><p>Meaning of <em>arg</em></p></th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><p><a class="reference internal" href="#c.PyTrace_CALL" title="PyTrace_CALL"><code class="xref c c-data docutils literal notranslate"><span class="pre">PyTrace_CALL</span></code></a></p></td>
<td><p>Always <a class="reference internal" href="none.html#c.Py_None" title="Py_None"><code class="xref c c-data docutils literal notranslate"><span class="pre">Py_None</span></code></a>.</p></td>
</tr>
<tr class="row-odd"><td><p><a class="reference internal" href="#c.PyTrace_EXCEPTION" title="PyTrace_EXCEPTION"><code class="xref c c-data docutils literal notranslate"><span class="pre">PyTrace_EXCEPTION</span></code></a></p></td>
<td><p>Exception information as returned by
<a class="reference internal" href="../library/sys.html#sys.exc_info" title="sys.exc_info"><code class="xref py py-func docutils literal notranslate"><span class="pre">sys.exc_info()</span></code></a>.</p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="#c.PyTrace_LINE" title="PyTrace_LINE"><code class="xref c c-data docutils literal notranslate"><span class="pre">PyTrace_LINE</span></code></a></p></td>
<td><p>Always <a class="reference internal" href="none.html#c.Py_None" title="Py_None"><code class="xref c c-data docutils literal notranslate"><span class="pre">Py_None</span></code></a>.</p></td>
</tr>
<tr class="row-odd"><td><p><a class="reference internal" href="#c.PyTrace_RETURN" title="PyTrace_RETURN"><code class="xref c c-data docutils literal notranslate"><span class="pre">PyTrace_RETURN</span></code></a></p></td>
<td><p>Value being returned to the caller,
or <code class="docutils literal notranslate"><span class="pre">NULL</span></code> if caused by an exception.</p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="#c.PyTrace_C_CALL" title="PyTrace_C_CALL"><code class="xref c c-data docutils literal notranslate"><span class="pre">PyTrace_C_CALL</span></code></a></p></td>
<td><p>Function object being called.</p></td>
</tr>
<tr class="row-odd"><td><p><a class="reference internal" href="#c.PyTrace_C_EXCEPTION" title="PyTrace_C_EXCEPTION"><code class="xref c c-data docutils literal notranslate"><span class="pre">PyTrace_C_EXCEPTION</span></code></a></p></td>
<td><p>Function object being called.</p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="#c.PyTrace_C_RETURN" title="PyTrace_C_RETURN"><code class="xref c c-data docutils literal notranslate"><span class="pre">PyTrace_C_RETURN</span></code></a></p></td>
<td><p>Function object being called.</p></td>
</tr>
<tr class="row-odd"><td><p><a class="reference internal" href="#c.PyTrace_OPCODE" title="PyTrace_OPCODE"><code class="xref c c-data docutils literal notranslate"><span class="pre">PyTrace_OPCODE</span></code></a></p></td>
<td><p>Always <a class="reference internal" href="none.html#c.Py_None" title="Py_None"><code class="xref c c-data docutils literal notranslate"><span class="pre">Py_None</span></code></a>.</p></td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="c var">
<dt class="sig sig-object c" id="c.PyTrace_CALL">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyTrace_CALL</span></span></span><a class="headerlink" href="#c.PyTrace_CALL" title="Link to this definition">¶</a><br /></dt>
<dd><p>The value of the <em>what</em> parameter to a <a class="reference internal" href="#c.Py_tracefunc" title="Py_tracefunc"><code class="xref c c-type docutils literal notranslate"><span class="pre">Py_tracefunc</span></code></a> function when a new
call to a function or method is being reported, or a new entry into a generator.
Note that the creation of the iterator for a generator function is not reported
as there is no control transfer to the Python bytecode in the corresponding
frame.</p>
</dd></dl>
<dl class="c var">
<dt class="sig sig-object c" id="c.PyTrace_EXCEPTION">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyTrace_EXCEPTION</span></span></span><a class="headerlink" href="#c.PyTrace_EXCEPTION" title="Link to this definition">¶</a><br /></dt>
<dd><p>The value of the <em>what</em> parameter to a <a class="reference internal" href="#c.Py_tracefunc" title="Py_tracefunc"><code class="xref c c-type docutils literal notranslate"><span class="pre">Py_tracefunc</span></code></a> function when an
exception has been raised. The callback function is called with this value for
<em>what</em> when after any bytecode is processed after which the exception becomes
set within the frame being executed. The effect of this is that as exception
propagation causes the Python stack to unwind, the callback is called upon
return to each frame as the exception propagates. Only trace functions receives
these events; they are not needed by the profiler.</p>
</dd></dl>
<dl class="c var">
<dt class="sig sig-object c" id="c.PyTrace_LINE">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyTrace_LINE</span></span></span><a class="headerlink" href="#c.PyTrace_LINE" title="Link to this definition">¶</a><br /></dt>
<dd><p>The value passed as the <em>what</em> parameter to a <a class="reference internal" href="#c.Py_tracefunc" title="Py_tracefunc"><code class="xref c c-type docutils literal notranslate"><span class="pre">Py_tracefunc</span></code></a> function
(but not a profiling function) when a line-number event is being reported.
It may be disabled for a frame by setting <a class="reference internal" href="../reference/datamodel.html#frame.f_trace_lines" title="frame.f_trace_lines"><code class="xref py py-attr docutils literal notranslate"><span class="pre">f_trace_lines</span></code></a> to
<em>0</em> on that frame.</p>
</dd></dl>
<dl class="c var">
<dt class="sig sig-object c" id="c.PyTrace_RETURN">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyTrace_RETURN</span></span></span><a class="headerlink" href="#c.PyTrace_RETURN" title="Link to this definition">¶</a><br /></dt>
<dd><p>The value for the <em>what</em> parameter to <a class="reference internal" href="#c.Py_tracefunc" title="Py_tracefunc"><code class="xref c c-type docutils literal notranslate"><span class="pre">Py_tracefunc</span></code></a> functions when a
call is about to return.</p>
</dd></dl>
<dl class="c var">
<dt class="sig sig-object c" id="c.PyTrace_C_CALL">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyTrace_C_CALL</span></span></span><a class="headerlink" href="#c.PyTrace_C_CALL" title="Link to this definition">¶</a><br /></dt>
<dd><p>The value for the <em>what</em> parameter to <a class="reference internal" href="#c.Py_tracefunc" title="Py_tracefunc"><code class="xref c c-type docutils literal notranslate"><span class="pre">Py_tracefunc</span></code></a> functions when a C
function is about to be called.</p>
</dd></dl>
<dl class="c var">
<dt class="sig sig-object c" id="c.PyTrace_C_EXCEPTION">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyTrace_C_EXCEPTION</span></span></span><a class="headerlink" href="#c.PyTrace_C_EXCEPTION" title="Link to this definition">¶</a><br /></dt>
<dd><p>The value for the <em>what</em> parameter to <a class="reference internal" href="#c.Py_tracefunc" title="Py_tracefunc"><code class="xref c c-type docutils literal notranslate"><span class="pre">Py_tracefunc</span></code></a> functions when a C
function has raised an exception.</p>
</dd></dl>
<dl class="c var">
<dt class="sig sig-object c" id="c.PyTrace_C_RETURN">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyTrace_C_RETURN</span></span></span><a class="headerlink" href="#c.PyTrace_C_RETURN" title="Link to this definition">¶</a><br /></dt>
<dd><p>The value for the <em>what</em> parameter to <a class="reference internal" href="#c.Py_tracefunc" title="Py_tracefunc"><code class="xref c c-type docutils literal notranslate"><span class="pre">Py_tracefunc</span></code></a> functions when a C
function has returned.</p>
</dd></dl>
<dl class="c var">
<dt class="sig sig-object c" id="c.PyTrace_OPCODE">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyTrace_OPCODE</span></span></span><a class="headerlink" href="#c.PyTrace_OPCODE" title="Link to this definition">¶</a><br /></dt>
<dd><p>The value for the <em>what</em> parameter to <a class="reference internal" href="#c.Py_tracefunc" title="Py_tracefunc"><code class="xref c c-type docutils literal notranslate"><span class="pre">Py_tracefunc</span></code></a> functions (but not
profiling functions) when a new opcode is about to be executed. This event is
not emitted by default: it must be explicitly requested by setting
<a class="reference internal" href="../reference/datamodel.html#frame.f_trace_opcodes" title="frame.f_trace_opcodes"><code class="xref py py-attr docutils literal notranslate"><span class="pre">f_trace_opcodes</span></code></a> to <em>1</em> on the frame.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyEval_SetProfile">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyEval_SetProfile</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.Py_tracefunc" title="Py_tracefunc"><span class="n"><span class="pre">Py_tracefunc</span></span></a><span class="w"> </span><span class="n"><span class="pre">func</span></span>, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">obj</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyEval_SetProfile" title="Link to this definition">¶</a><br /></dt>
<dd><p>Set the profiler function to <em>func</em>. The <em>obj</em> parameter is passed to the
function as its first parameter, and may be any Python object, or <code class="docutils literal notranslate"><span class="pre">NULL</span></code>. If
the profile function needs to maintain state, using a different value for <em>obj</em>
for each thread provides a convenient and thread-safe place to store it. The
profile function is called for all monitored events except <a class="reference internal" href="#c.PyTrace_LINE" title="PyTrace_LINE"><code class="xref c c-data docutils literal notranslate"><span class="pre">PyTrace_LINE</span></code></a>
<a class="reference internal" href="#c.PyTrace_OPCODE" title="PyTrace_OPCODE"><code class="xref c c-data docutils literal notranslate"><span class="pre">PyTrace_OPCODE</span></code></a> and <a class="reference internal" href="#c.PyTrace_EXCEPTION" title="PyTrace_EXCEPTION"><code class="xref c c-data docutils literal notranslate"><span class="pre">PyTrace_EXCEPTION</span></code></a>.</p>
<p>See also the <a class="reference internal" href="../library/sys.html#sys.setprofile" title="sys.setprofile"><code class="xref py py-func docutils literal notranslate"><span class="pre">sys.setprofile()</span></code></a> function.</p>
<p>The caller must have an <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a>.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyEval_SetProfileAllThreads">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyEval_SetProfileAllThreads</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.Py_tracefunc" title="Py_tracefunc"><span class="n"><span class="pre">Py_tracefunc</span></span></a><span class="w"> </span><span class="n"><span class="pre">func</span></span>, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">obj</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyEval_SetProfileAllThreads" title="Link to this definition">¶</a><br /></dt>
<dd><p>Like <a class="reference internal" href="#c.PyEval_SetProfile" title="PyEval_SetProfile"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyEval_SetProfile()</span></code></a> but sets the profile function in all running threads
belonging to the current interpreter instead of the setting it only on the current thread.</p>
<p>The caller must have an <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a>.</p>
<p>As <a class="reference internal" href="#c.PyEval_SetProfile" title="PyEval_SetProfile"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyEval_SetProfile()</span></code></a>, this function ignores any exceptions raised while
setting the profile functions in all threads.</p>
</dd></dl>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.12.</span></p>
</div>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyEval_SetTrace">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyEval_SetTrace</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.Py_tracefunc" title="Py_tracefunc"><span class="n"><span class="pre">Py_tracefunc</span></span></a><span class="w"> </span><span class="n"><span class="pre">func</span></span>, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">obj</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyEval_SetTrace" title="Link to this definition">¶</a><br /></dt>
<dd><p>Set the tracing function to <em>func</em>. This is similar to
<a class="reference internal" href="#c.PyEval_SetProfile" title="PyEval_SetProfile"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyEval_SetProfile()</span></code></a>, except the tracing function does receive line-number
events and per-opcode events, but does not receive any event related to C function
objects being called. Any trace function registered using <a class="reference internal" href="#c.PyEval_SetTrace" title="PyEval_SetTrace"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyEval_SetTrace()</span></code></a>
will not receive <a class="reference internal" href="#c.PyTrace_C_CALL" title="PyTrace_C_CALL"><code class="xref c c-data docutils literal notranslate"><span class="pre">PyTrace_C_CALL</span></code></a>, <a class="reference internal" href="#c.PyTrace_C_EXCEPTION" title="PyTrace_C_EXCEPTION"><code class="xref c c-data docutils literal notranslate"><span class="pre">PyTrace_C_EXCEPTION</span></code></a> or
<a class="reference internal" href="#c.PyTrace_C_RETURN" title="PyTrace_C_RETURN"><code class="xref c c-data docutils literal notranslate"><span class="pre">PyTrace_C_RETURN</span></code></a> as a value for the <em>what</em> parameter.</p>
<p>See also the <a class="reference internal" href="../library/sys.html#sys.settrace" title="sys.settrace"><code class="xref py py-func docutils literal notranslate"><span class="pre">sys.settrace()</span></code></a> function.</p>
<p>The caller must have an <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a>.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyEval_SetTraceAllThreads">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyEval_SetTraceAllThreads</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.Py_tracefunc" title="Py_tracefunc"><span class="n"><span class="pre">Py_tracefunc</span></span></a><span class="w"> </span><span class="n"><span class="pre">func</span></span>, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">obj</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyEval_SetTraceAllThreads" title="Link to this definition">¶</a><br /></dt>
<dd><p>Like <a class="reference internal" href="#c.PyEval_SetTrace" title="PyEval_SetTrace"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyEval_SetTrace()</span></code></a> but sets the tracing function in all running threads
belonging to the current interpreter instead of the setting it only on the current thread.</p>
<p>The caller must have an <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a>.</p>
<p>As <a class="reference internal" href="#c.PyEval_SetTrace" title="PyEval_SetTrace"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyEval_SetTrace()</span></code></a>, this function ignores any exceptions raised while
setting the trace functions in all threads.</p>
</dd></dl>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.12.</span></p>
</div>
</section>
<section id="reference-tracing">
<h2>Reference tracing<a class="headerlink" href="#reference-tracing" title="Link to this heading">¶</a></h2>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.13.</span></p>
</div>
<dl class="c type">
<dt class="sig sig-object c" id="c.PyRefTracer">
<span class="k"><span class="pre">typedef</span></span><span class="w"> </span><span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="p"><span class="pre">(</span></span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">PyRefTracer</span></span></span><span class="p"><span class="pre">)</span></span><span class="p"><span class="pre">(</span></span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="p"><span class="pre">*</span></span><span class="p"><span class="pre">,</span></span><span class="w"> </span><span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">event</span></span><span class="p"><span class="pre">,</span></span><span class="w"> </span><span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">data</span></span><span class="p"><span class="pre">)</span></span><a class="headerlink" href="#c.PyRefTracer" title="Link to this definition">¶</a><br /></dt>
<dd><p>The type of the trace function registered using <a class="reference internal" href="#c.PyRefTracer_SetTracer" title="PyRefTracer_SetTracer"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyRefTracer_SetTracer()</span></code></a>.
The first parameter is a Python object that has been just created (when <strong>event</strong>
is set to <a class="reference internal" href="#c.PyRefTracer_CREATE" title="PyRefTracer_CREATE"><code class="xref c c-data docutils literal notranslate"><span class="pre">PyRefTracer_CREATE</span></code></a>) or about to be destroyed (when <strong>event</strong>
is set to <a class="reference internal" href="#c.PyRefTracer_DESTROY" title="PyRefTracer_DESTROY"><code class="xref c c-data docutils literal notranslate"><span class="pre">PyRefTracer_DESTROY</span></code></a>). The <strong>data</strong> argument is the opaque pointer
that was provided when <a class="reference internal" href="#c.PyRefTracer_SetTracer" title="PyRefTracer_SetTracer"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyRefTracer_SetTracer()</span></code></a> was called.</p>
</dd></dl>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.13.</span></p>
</div>
<dl class="c var">
<dt class="sig sig-object c" id="c.PyRefTracer_CREATE">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyRefTracer_CREATE</span></span></span><a class="headerlink" href="#c.PyRefTracer_CREATE" title="Link to this definition">¶</a><br /></dt>
<dd><p>The value for the <em>event</em> parameter to <a class="reference internal" href="#c.PyRefTracer" title="PyRefTracer"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyRefTracer</span></code></a> functions when a Python
object has been created.</p>
</dd></dl>
<dl class="c var">
<dt class="sig sig-object c" id="c.PyRefTracer_DESTROY">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyRefTracer_DESTROY</span></span></span><a class="headerlink" href="#c.PyRefTracer_DESTROY" title="Link to this definition">¶</a><br /></dt>
<dd><p>The value for the <em>event</em> parameter to <a class="reference internal" href="#c.PyRefTracer" title="PyRefTracer"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyRefTracer</span></code></a> functions when a Python
object has been destroyed.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyRefTracer_SetTracer">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyRefTracer_SetTracer</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.PyRefTracer" title="PyRefTracer"><span class="n"><span class="pre">PyRefTracer</span></span></a><span class="w"> </span><span class="n"><span class="pre">tracer</span></span>, <span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">data</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyRefTracer_SetTracer" title="Link to this definition">¶</a><br /></dt>
<dd><p>Register a reference tracer function. The function will be called when a new
Python has been created or when an object is going to be destroyed. If
<strong>data</strong> is provided it must be an opaque pointer that will be provided when
the tracer function is called. Return <code class="docutils literal notranslate"><span class="pre">0</span></code> on success. Set an exception and
return <code class="docutils literal notranslate"><span class="pre">-1</span></code> on error.</p>
<p>Not that tracer functions <strong>must not</strong> create Python objects inside or
otherwise the call will be re-entrant. The tracer also <strong>must not</strong> clear
any existing exception or set an exception. A <a class="reference internal" href="../glossary.html#term-thread-state"><span class="xref std std-term">thread state</span></a> will be active
every time the tracer function is called.</p>
<p>There must be an <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a> when calling this function.</p>
</dd></dl>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.13.</span></p>
</div>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyRefTracer_GetTracer">
<a class="reference internal" href="#c.PyRefTracer" title="PyRefTracer"><span class="n"><span class="pre">PyRefTracer</span></span></a><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyRefTracer_GetTracer</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">data</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyRefTracer_GetTracer" title="Link to this definition">¶</a><br /></dt>
<dd><p>Get the registered reference tracer function and the value of the opaque data
pointer that was registered when <a class="reference internal" href="#c.PyRefTracer_SetTracer" title="PyRefTracer_SetTracer"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyRefTracer_SetTracer()</span></code></a> was called.
If no tracer was registered this function will return NULL and will set the
<strong>data</strong> pointer to NULL.</p>
<p>There must be an <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached thread state</span></a> when calling this function.</p>
</dd></dl>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.13.</span></p>
</div>
</section>
<section id="advanced-debugger-support">
<span id="advanced-debugging"></span><h2>Advanced Debugger Support<a class="headerlink" href="#advanced-debugger-support" title="Link to this heading">¶</a></h2>
<p>These functions are only intended to be used by advanced debugging tools.</p>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyInterpreterState_Head">
<a class="reference internal" href="#c.PyInterpreterState" title="PyInterpreterState"><span class="n"><span class="pre">PyInterpreterState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">PyInterpreterState_Head</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyInterpreterState_Head" title="Link to this definition">¶</a><br /></dt>
<dd><p>Return the interpreter state object at the head of the list of all such objects.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyInterpreterState_Main">
<a class="reference internal" href="#c.PyInterpreterState" title="PyInterpreterState"><span class="n"><span class="pre">PyInterpreterState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">PyInterpreterState_Main</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyInterpreterState_Main" title="Link to this definition">¶</a><br /></dt>
<dd><p>Return the main interpreter state object.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyInterpreterState_Next">
<a class="reference internal" href="#c.PyInterpreterState" title="PyInterpreterState"><span class="n"><span class="pre">PyInterpreterState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">PyInterpreterState_Next</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.PyInterpreterState" title="PyInterpreterState"><span class="n"><span class="pre">PyInterpreterState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">interp</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyInterpreterState_Next" title="Link to this definition">¶</a><br /></dt>
<dd><p>Return the next interpreter state object after <em>interp</em> from the list of all
such objects.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyInterpreterState_ThreadHead">
<a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><span class="n"><span class="pre">PyThreadState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">PyInterpreterState_ThreadHead</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.PyInterpreterState" title="PyInterpreterState"><span class="n"><span class="pre">PyInterpreterState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">interp</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyInterpreterState_ThreadHead" title="Link to this definition">¶</a><br /></dt>
<dd><p>Return the pointer to the first <a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyThreadState</span></code></a> object in the list of
threads associated with the interpreter <em>interp</em>.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyThreadState_Next">
<a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><span class="n"><span class="pre">PyThreadState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">PyThreadState_Next</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><span class="n"><span class="pre">PyThreadState</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">tstate</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyThreadState_Next" title="Link to this definition">¶</a><br /></dt>
<dd><p>Return the next thread state object after <em>tstate</em> from the list of all such
objects belonging to the same <a class="reference internal" href="#c.PyInterpreterState" title="PyInterpreterState"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyInterpreterState</span></code></a> object.</p>
</dd></dl>
</section>
<section id="thread-local-storage-support">
<span id="thread-local-storage"></span><h2>Thread Local Storage Support<a class="headerlink" href="#thread-local-storage-support" title="Link to this heading">¶</a></h2>
<p>The Python interpreter provides low-level support for thread-local storage
(TLS) which wraps the underlying native TLS implementation to support the
Python-level thread local storage API (<a class="reference internal" href="../library/threading.html#threading.local" title="threading.local"><code class="xref py py-class docutils literal notranslate"><span class="pre">threading.local</span></code></a>). The
CPython C level APIs are similar to those offered by pthreads and Windows:
use a thread key and functions to associate a <span class="c-expr sig sig-inline c"><span class="kt">void</span><span class="p">*</span></span> value per
thread.</p>
<p>A <a class="reference internal" href="../glossary.html#term-thread-state"><span class="xref std std-term">thread state</span></a> does <em>not</em> need to be <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">attached</span></a>
when calling these functions; they suppl their own locking.</p>
<p>Note that <code class="file docutils literal notranslate"><span class="pre">Python.h</span></code> does not include the declaration of the TLS APIs,
you need to include <code class="file docutils literal notranslate"><span class="pre">pythread.h</span></code> to use thread-local storage.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>None of these API functions handle memory management on behalf of the
<span class="c-expr sig sig-inline c"><span class="kt">void</span><span class="p">*</span></span> values. You need to allocate and deallocate them yourself.
If the <span class="c-expr sig sig-inline c"><span class="kt">void</span><span class="p">*</span></span> values happen to be <span class="c-expr sig sig-inline c"><a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n">PyObject</span></a><span class="p">*</span></span>, these
functions don’t do refcount operations on them either.</p>
</div>
<section id="thread-specific-storage-tss-api">
<span id="thread-specific-storage-api"></span><h3>Thread Specific Storage (TSS) API<a class="headerlink" href="#thread-specific-storage-tss-api" title="Link to this heading">¶</a></h3>
<p>TSS API is introduced to supersede the use of the existing TLS API within the
CPython interpreter. This API uses a new type <a class="reference internal" href="#c.Py_tss_t" title="Py_tss_t"><code class="xref c c-type docutils literal notranslate"><span class="pre">Py_tss_t</span></code></a> instead of
<span class="c-expr sig sig-inline c"><span class="kt">int</span></span> to represent thread keys.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.7.</span></p>
</div>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<p>“A New C-API for Thread-Local Storage in CPython” (<span class="target" id="index-47"></span><a class="pep reference external" href="https://peps.python.org/pep-0539/"><strong>PEP 539</strong></a>)</p>
</div>
<dl class="c type">
<dt class="sig sig-object c" id="c.Py_tss_t">
<span class="k"><span class="pre">type</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_tss_t</span></span></span><a class="headerlink" href="#c.Py_tss_t" title="Link to this definition">¶</a><br /></dt>
<dd><p>This data structure represents the state of a thread key, the definition of
which may depend on the underlying TLS implementation, and it has an
internal field representing the key’s initialization state. There are no
public members in this structure.</p>
<p>When <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Py_LIMITED_API</span></a> is not defined, static allocation of
this type by <a class="reference internal" href="#c.Py_tss_NEEDS_INIT" title="Py_tss_NEEDS_INIT"><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_tss_NEEDS_INIT</span></code></a> is allowed.</p>
</dd></dl>
<dl class="c macro">
<dt class="sig sig-object c" id="c.Py_tss_NEEDS_INIT">
<span class="sig-name descname"><span class="n"><span class="pre">Py_tss_NEEDS_INIT</span></span></span><a class="headerlink" href="#c.Py_tss_NEEDS_INIT" title="Link to this definition">¶</a><br /></dt>
<dd><p>This macro expands to the initializer for <a class="reference internal" href="#c.Py_tss_t" title="Py_tss_t"><code class="xref c c-type docutils literal notranslate"><span class="pre">Py_tss_t</span></code></a> variables.
Note that this macro won’t be defined with <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Py_LIMITED_API</span></a>.</p>
</dd></dl>
<section id="dynamic-allocation">
<h4>Dynamic Allocation<a class="headerlink" href="#dynamic-allocation" title="Link to this heading">¶</a></h4>
<p>Dynamic allocation of the <a class="reference internal" href="#c.Py_tss_t" title="Py_tss_t"><code class="xref c c-type docutils literal notranslate"><span class="pre">Py_tss_t</span></code></a>, required in extension modules
built with <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Py_LIMITED_API</span></a>, where static allocation of this type
is not possible due to its implementation being opaque at build time.</p>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyThread_tss_alloc">
<a class="reference internal" href="#c.Py_tss_t" title="Py_tss_t"><span class="n"><span class="pre">Py_tss_t</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">PyThread_tss_alloc</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyThread_tss_alloc" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.7.</em><p>Return a value which is the same state as a value initialized with
<a class="reference internal" href="#c.Py_tss_NEEDS_INIT" title="Py_tss_NEEDS_INIT"><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_tss_NEEDS_INIT</span></code></a>, or <code class="docutils literal notranslate"><span class="pre">NULL</span></code> in the case of dynamic allocation
failure.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyThread_tss_free">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyThread_tss_free</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.Py_tss_t" title="Py_tss_t"><span class="n"><span class="pre">Py_tss_t</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">key</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyThread_tss_free" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.7.</em><p>Free the given <em>key</em> allocated by <a class="reference internal" href="#c.PyThread_tss_alloc" title="PyThread_tss_alloc"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyThread_tss_alloc()</span></code></a>, after
first calling <a class="reference internal" href="#c.PyThread_tss_delete" title="PyThread_tss_delete"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyThread_tss_delete()</span></code></a> to ensure any associated
thread locals have been unassigned. This is a no-op if the <em>key</em>
argument is <code class="docutils literal notranslate"><span class="pre">NULL</span></code>.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>A freed key becomes a dangling pointer. You should reset the key to
<code class="docutils literal notranslate"><span class="pre">NULL</span></code>.</p>
</div>
</dd></dl>
</section>
<section id="methods">
<h4>Methods<a class="headerlink" href="#methods" title="Link to this heading">¶</a></h4>
<p>The parameter <em>key</em> of these functions must not be <code class="docutils literal notranslate"><span class="pre">NULL</span></code>. Moreover, the
behaviors of <a class="reference internal" href="#c.PyThread_tss_set" title="PyThread_tss_set"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyThread_tss_set()</span></code></a> and <a class="reference internal" href="#c.PyThread_tss_get" title="PyThread_tss_get"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyThread_tss_get()</span></code></a> are
undefined if the given <a class="reference internal" href="#c.Py_tss_t" title="Py_tss_t"><code class="xref c c-type docutils literal notranslate"><span class="pre">Py_tss_t</span></code></a> has not been initialized by
<a class="reference internal" href="#c.PyThread_tss_create" title="PyThread_tss_create"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyThread_tss_create()</span></code></a>.</p>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyThread_tss_is_created">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyThread_tss_is_created</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.Py_tss_t" title="Py_tss_t"><span class="n"><span class="pre">Py_tss_t</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">key</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyThread_tss_is_created" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.7.</em><p>Return a non-zero value if the given <a class="reference internal" href="#c.Py_tss_t" title="Py_tss_t"><code class="xref c c-type docutils literal notranslate"><span class="pre">Py_tss_t</span></code></a> has been initialized
by <a class="reference internal" href="#c.PyThread_tss_create" title="PyThread_tss_create"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyThread_tss_create()</span></code></a>.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyThread_tss_create">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyThread_tss_create</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.Py_tss_t" title="Py_tss_t"><span class="n"><span class="pre">Py_tss_t</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">key</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyThread_tss_create" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.7.</em><p>Return a zero value on successful initialization of a TSS key. The behavior
is undefined if the value pointed to by the <em>key</em> argument is not
initialized by <a class="reference internal" href="#c.Py_tss_NEEDS_INIT" title="Py_tss_NEEDS_INIT"><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_tss_NEEDS_INIT</span></code></a>. This function can be called
repeatedly on the same key – calling it on an already initialized key is a
no-op and immediately returns success.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyThread_tss_delete">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyThread_tss_delete</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.Py_tss_t" title="Py_tss_t"><span class="n"><span class="pre">Py_tss_t</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">key</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyThread_tss_delete" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.7.</em><p>Destroy a TSS key to forget the values associated with the key across all
threads, and change the key’s initialization state to uninitialized. A
destroyed key is able to be initialized again by
<a class="reference internal" href="#c.PyThread_tss_create" title="PyThread_tss_create"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyThread_tss_create()</span></code></a>. This function can be called repeatedly on
the same key – calling it on an already destroyed key is a no-op.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyThread_tss_set">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyThread_tss_set</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.Py_tss_t" title="Py_tss_t"><span class="n"><span class="pre">Py_tss_t</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">key</span></span>, <span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">value</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyThread_tss_set" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.7.</em><p>Return a zero value to indicate successfully associating a <span class="c-expr sig sig-inline c"><span class="kt">void</span><span class="p">*</span></span>
value with a TSS key in the current thread. Each thread has a distinct
mapping of the key to a <span class="c-expr sig sig-inline c"><span class="kt">void</span><span class="p">*</span></span> value.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyThread_tss_get">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">PyThread_tss_get</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.Py_tss_t" title="Py_tss_t"><span class="n"><span class="pre">Py_tss_t</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">key</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyThread_tss_get" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.7.</em><p>Return the <span class="c-expr sig sig-inline c"><span class="kt">void</span><span class="p">*</span></span> value associated with a TSS key in the current
thread. This returns <code class="docutils literal notranslate"><span class="pre">NULL</span></code> if no value is associated with the key in the
current thread.</p>
</dd></dl>
</section>
</section>
<section id="thread-local-storage-tls-api">
<span id="thread-local-storage-api"></span><h3>Thread Local Storage (TLS) API<a class="headerlink" href="#thread-local-storage-tls-api" title="Link to this heading">¶</a></h3>
<div class="deprecated">
<p><span class="versionmodified deprecated">Deprecated since version 3.7: </span>This API is superseded by
<a class="reference internal" href="#thread-specific-storage-api"><span class="std std-ref">Thread Specific Storage (TSS) API</span></a>.</p>
</div>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>This version of the API does not support platforms where the native TLS key
is defined in a way that cannot be safely cast to <code class="docutils literal notranslate"><span class="pre">int</span></code>. On such platforms,
<a class="reference internal" href="#c.PyThread_create_key" title="PyThread_create_key"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyThread_create_key()</span></code></a> will return immediately with a failure status,
and the other TLS functions will all be no-ops on such platforms.</p>
</div>
<p>Due to the compatibility problem noted above, this version of the API should not
be used in new code.</p>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyThread_create_key">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyThread_create_key</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyThread_create_key" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em></dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyThread_delete_key">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyThread_delete_key</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">key</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyThread_delete_key" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em></dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyThread_set_key_value">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyThread_set_key_value</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">key</span></span>, <span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">value</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyThread_set_key_value" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em></dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyThread_get_key_value">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">PyThread_get_key_value</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">key</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyThread_get_key_value" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em></dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyThread_delete_key_value">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyThread_delete_key_value</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">key</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyThread_delete_key_value" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em></dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyThread_ReInitTLS">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyThread_ReInitTLS</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyThread_ReInitTLS" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em></dd></dl>
</section>
</section>
<section id="synchronization-primitives">
<h2>Synchronization Primitives<a class="headerlink" href="#synchronization-primitives" title="Link to this heading">¶</a></h2>
<p>The C-API provides a basic mutual exclusion lock.</p>
<dl class="c type">
<dt class="sig sig-object c" id="c.PyMutex">
<span class="k"><span class="pre">type</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyMutex</span></span></span><a class="headerlink" href="#c.PyMutex" title="Link to this definition">¶</a><br /></dt>
<dd><p>A mutual exclusion lock. The <code class="xref c c-type docutils literal notranslate"><span class="pre">PyMutex</span></code> should be initialized to
zero to represent the unlocked state. For example:</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="n">PyMutex</span><span class="w"> </span><span class="n">mutex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="mi">0</span><span class="p">};</span>
</pre></div>
</div>
<p>Instances of <code class="xref c c-type docutils literal notranslate"><span class="pre">PyMutex</span></code> should not be copied or moved. Both the
contents and address of a <code class="xref c c-type docutils literal notranslate"><span class="pre">PyMutex</span></code> are meaningful, and it must
remain at a fixed, writable location in memory.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>A <code class="xref c c-type docutils literal notranslate"><span class="pre">PyMutex</span></code> currently occupies one byte, but the size should be
considered unstable. The size may change in future Python releases
without a deprecation period.</p>
</div>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.13.</span></p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyMutex_Lock">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyMutex_Lock</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.PyMutex" title="PyMutex"><span class="n"><span class="pre">PyMutex</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">m</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyMutex_Lock" title="Link to this definition">¶</a><br /></dt>
<dd><p>Lock mutex <em>m</em>. If another thread has already locked it, the calling
thread will block until the mutex is unlocked. While blocked, the thread
will temporarily detach the <a class="reference internal" href="../glossary.html#term-attached-thread-state"><span class="xref std std-term">thread state</span></a> if one exists.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.13.</span></p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyMutex_Unlock">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyMutex_Unlock</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.PyMutex" title="PyMutex"><span class="n"><span class="pre">PyMutex</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">m</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyMutex_Unlock" title="Link to this definition">¶</a><br /></dt>
<dd><p>Unlock mutex <em>m</em>. The mutex must be locked — otherwise, the function will
issue a fatal error.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.13.</span></p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyMutex_IsLocked">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyMutex_IsLocked</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.PyMutex" title="PyMutex"><span class="n"><span class="pre">PyMutex</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">m</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyMutex_IsLocked" title="Link to this definition">¶</a><br /></dt>
<dd><p>Returns non-zero if the mutex <em>m</em> is currently locked, zero otherwise.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>This function is intended for use in assertions and debugging only and
should not be used to make concurrency control decisions, as the lock
state may change immediately after the check.</p>
</div>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.14.</span></p>
</div>
</dd></dl>
<section id="python-critical-section-api">
<span id="id3"></span><h3>Python Critical Section API<a class="headerlink" href="#python-critical-section-api" title="Link to this heading">¶</a></h3>
<p>The critical section API provides a deadlock avoidance layer on top of
per-object locks for <a class="reference internal" href="../glossary.html#term-free-threading"><span class="xref std std-term">free-threaded</span></a> CPython. They are
intended to replace reliance on the <a class="reference internal" href="../glossary.html#term-global-interpreter-lock"><span class="xref std std-term">global interpreter lock</span></a>, and are
no-ops in versions of Python with the global interpreter lock.</p>
<p>Critical sections are intended to be used for custom types implemented
in C-API extensions. They should generally not be used with built-in types like
<a class="reference internal" href="../library/stdtypes.html#list" title="list"><code class="xref py py-class docutils literal notranslate"><span class="pre">list</span></code></a> and <a class="reference internal" href="../library/stdtypes.html#dict" title="dict"><code class="xref py py-class docutils literal notranslate"><span class="pre">dict</span></code></a> because their public C-APIs
already use critical sections internally, with the notable
exception of <a class="reference internal" href="dict.html#c.PyDict_Next" title="PyDict_Next"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyDict_Next()</span></code></a>, which requires critical section
to be acquired externally.</p>
<p>Critical sections avoid deadlocks by implicitly suspending active critical
sections, hence, they do not provide exclusive access such as provided by
traditional locks like <a class="reference internal" href="#c.PyMutex" title="PyMutex"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyMutex</span></code></a>. When a critical section is started,
the per-object lock for the object is acquired. If the code executed inside the
critical section calls C-API functions then it can suspend the critical section thereby
releasing the per-object lock, so other threads can acquire the per-object lock
for the same object.</p>
<p>Variants that accept <a class="reference internal" href="#c.PyMutex" title="PyMutex"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyMutex</span></code></a> pointers rather than Python objects are also
available. Use these variants to start a critical section in a situation where
there is no <a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyObject</span></code></a> – for example, when working with a C type that
does not extend or wrap <a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyObject</span></code></a> but still needs to call into the C
API in a manner that might lead to deadlocks.</p>
<p>The functions and structs used by the macros are exposed for cases
where C macros are not available. They should only be used as in the
given macro expansions. Note that the sizes and contents of the structures may
change in future Python versions.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>Operations that need to lock two objects at once must use
<a class="reference internal" href="#c.Py_BEGIN_CRITICAL_SECTION2" title="Py_BEGIN_CRITICAL_SECTION2"><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_BEGIN_CRITICAL_SECTION2</span></code></a>. You <em>cannot</em> use nested critical
sections to lock more than one object at once, because the inner critical
section may suspend the outer critical sections. This API does not provide
a way to lock more than two objects at once.</p>
</div>
<p>Example usage:</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="k">static</span><span class="w"> </span><span class="n">PyObject</span><span class="w"> </span><span class="o">*</span>
<span class="nf">set_field</span><span class="p">(</span><span class="n">MyObject</span><span class="w"> </span><span class="o">*</span><span class="n">self</span><span class="p">,</span><span class="w"> </span><span class="n">PyObject</span><span class="w"> </span><span class="o">*</span><span class="n">value</span><span class="p">)</span>
<span class="p">{</span>
<span class="w"> </span><span class="n">Py_BEGIN_CRITICAL_SECTION</span><span class="p">(</span><span class="n">self</span><span class="p">);</span>
<span class="w"> </span><span class="n">Py_SETREF</span><span class="p">(</span><span class="n">self</span><span class="o">-></span><span class="n">field</span><span class="p">,</span><span class="w"> </span><span class="n">Py_XNewRef</span><span class="p">(</span><span class="n">value</span><span class="p">));</span>
<span class="w"> </span><span class="n">Py_END_CRITICAL_SECTION</span><span class="p">();</span>
<span class="w"> </span><span class="n">Py_RETURN_NONE</span><span class="p">;</span>
<span class="p">}</span>
</pre></div>
</div>
<p>In the above example, <a class="reference internal" href="refcounting.html#c.Py_SETREF" title="Py_SETREF"><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_SETREF</span></code></a> calls <a class="reference internal" href="refcounting.html#c.Py_DECREF" title="Py_DECREF"><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_DECREF</span></code></a>, which
can call arbitrary code through an object’s deallocation function. The critical
section API avoids potential deadlocks due to reentrancy and lock ordering
by allowing the runtime to temporarily suspend the critical section if the
code triggered by the finalizer blocks and calls <a class="reference internal" href="#c.PyEval_SaveThread" title="PyEval_SaveThread"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyEval_SaveThread()</span></code></a>.</p>
<dl class="c macro">
<dt class="sig sig-object c" id="c.Py_BEGIN_CRITICAL_SECTION">
<span class="sig-name descname"><span class="n"><span class="pre">Py_BEGIN_CRITICAL_SECTION</span></span></span><span class="sig-paren">(</span><span class="n"><span class="pre">op</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_BEGIN_CRITICAL_SECTION" title="Link to this definition">¶</a><br /></dt>
<dd><p>Acquires the per-object lock for the object <em>op</em> and begins a
critical section.</p>
<p>In the free-threaded build, this macro expands to:</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="p">{</span>
<span class="w"> </span><span class="n">PyCriticalSection</span><span class="w"> </span><span class="n">_py_cs</span><span class="p">;</span>
<span class="w"> </span><span class="n">PyCriticalSection_Begin</span><span class="p">(</span><span class="o">&</span><span class="n">_py_cs</span><span class="p">,</span><span class="w"> </span><span class="p">(</span><span class="n">PyObject</span><span class="o">*</span><span class="p">)(</span><span class="n">op</span><span class="p">))</span>
</pre></div>
</div>
<p>In the default build, this macro expands to <code class="docutils literal notranslate"><span class="pre">{</span></code>.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.13.</span></p>
</div>
</dd></dl>
<dl class="c macro">
<dt class="sig sig-object c" id="c.Py_BEGIN_CRITICAL_SECTION_MUTEX">
<span class="sig-name descname"><span class="n"><span class="pre">Py_BEGIN_CRITICAL_SECTION_MUTEX</span></span></span><span class="sig-paren">(</span><span class="n"><span class="pre">m</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_BEGIN_CRITICAL_SECTION_MUTEX" title="Link to this definition">¶</a><br /></dt>
<dd><p>Locks the mutex <em>m</em> and begins a critical section.</p>
<p>In the free-threaded build, this macro expands to:</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="p">{</span>
<span class="w"> </span><span class="n">PyCriticalSection</span><span class="w"> </span><span class="n">_py_cs</span><span class="p">;</span>
<span class="w"> </span><span class="n">PyCriticalSection_BeginMutex</span><span class="p">(</span><span class="o">&</span><span class="n">_py_cs</span><span class="p">,</span><span class="w"> </span><span class="n">m</span><span class="p">)</span>
</pre></div>
</div>
<p>Note that unlike <a class="reference internal" href="#c.Py_BEGIN_CRITICAL_SECTION" title="Py_BEGIN_CRITICAL_SECTION"><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_BEGIN_CRITICAL_SECTION</span></code></a>, there is no cast for
the argument of the macro - it must be a <a class="reference internal" href="#c.PyMutex" title="PyMutex"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyMutex</span></code></a> pointer.</p>
<p>On the default build, this macro expands to <code class="docutils literal notranslate"><span class="pre">{</span></code>.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.14.</span></p>
</div>
</dd></dl>
<dl class="c macro">
<dt class="sig sig-object c" id="c.Py_END_CRITICAL_SECTION">
<span class="sig-name descname"><span class="n"><span class="pre">Py_END_CRITICAL_SECTION</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_END_CRITICAL_SECTION" title="Link to this definition">¶</a><br /></dt>
<dd><p>Ends the critical section and releases the per-object lock.</p>
<p>In the free-threaded build, this macro expands to:</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="w"> </span><span class="n">PyCriticalSection_End</span><span class="p">(</span><span class="o">&</span><span class="n">_py_cs</span><span class="p">);</span>
<span class="p">}</span>
</pre></div>
</div>
<p>In the default build, this macro expands to <code class="docutils literal notranslate"><span class="pre">}</span></code>.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.13.</span></p>
</div>
</dd></dl>
<dl class="c macro">
<dt class="sig sig-object c" id="c.Py_BEGIN_CRITICAL_SECTION2">
<span class="sig-name descname"><span class="n"><span class="pre">Py_BEGIN_CRITICAL_SECTION2</span></span></span><span class="sig-paren">(</span><span class="n"><span class="pre">a</span></span>, <span class="n"><span class="pre">b</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_BEGIN_CRITICAL_SECTION2" title="Link to this definition">¶</a><br /></dt>
<dd><p>Acquires the per-objects locks for the objects <em>a</em> and <em>b</em> and begins a
critical section. The locks are acquired in a consistent order (lowest
address first) to avoid lock ordering deadlocks.</p>
<p>In the free-threaded build, this macro expands to:</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="p">{</span>
<span class="w"> </span><span class="n">PyCriticalSection2</span><span class="w"> </span><span class="n">_py_cs2</span><span class="p">;</span>
<span class="w"> </span><span class="n">PyCriticalSection2_Begin</span><span class="p">(</span><span class="o">&</span><span class="n">_py_cs2</span><span class="p">,</span><span class="w"> </span><span class="p">(</span><span class="n">PyObject</span><span class="o">*</span><span class="p">)(</span><span class="n">a</span><span class="p">),</span><span class="w"> </span><span class="p">(</span><span class="n">PyObject</span><span class="o">*</span><span class="p">)(</span><span class="n">b</span><span class="p">))</span>
</pre></div>
</div>
<p>In the default build, this macro expands to <code class="docutils literal notranslate"><span class="pre">{</span></code>.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.13.</span></p>
</div>
</dd></dl>
<dl class="c macro">
<dt class="sig sig-object c" id="c.Py_BEGIN_CRITICAL_SECTION2_MUTEX">
<span class="sig-name descname"><span class="n"><span class="pre">Py_BEGIN_CRITICAL_SECTION2_MUTEX</span></span></span><span class="sig-paren">(</span><span class="n"><span class="pre">m1</span></span>, <span class="n"><span class="pre">m2</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_BEGIN_CRITICAL_SECTION2_MUTEX" title="Link to this definition">¶</a><br /></dt>
<dd><p>Locks the mutexes <em>m1</em> and <em>m2</em> and begins a critical section.</p>
<p>In the free-threaded build, this macro expands to:</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="p">{</span>
<span class="w"> </span><span class="n">PyCriticalSection2</span><span class="w"> </span><span class="n">_py_cs2</span><span class="p">;</span>
<span class="w"> </span><span class="n">PyCriticalSection2_BeginMutex</span><span class="p">(</span><span class="o">&</span><span class="n">_py_cs2</span><span class="p">,</span><span class="w"> </span><span class="n">m1</span><span class="p">,</span><span class="w"> </span><span class="n">m2</span><span class="p">)</span>
</pre></div>
</div>
<p>Note that unlike <a class="reference internal" href="#c.Py_BEGIN_CRITICAL_SECTION2" title="Py_BEGIN_CRITICAL_SECTION2"><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_BEGIN_CRITICAL_SECTION2</span></code></a>, there is no cast for
the arguments of the macro - they must be <a class="reference internal" href="#c.PyMutex" title="PyMutex"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyMutex</span></code></a> pointers.</p>
<p>On the default build, this macro expands to <code class="docutils literal notranslate"><span class="pre">{</span></code>.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.14.</span></p>
</div>
</dd></dl>
<dl class="c macro">
<dt class="sig sig-object c" id="c.Py_END_CRITICAL_SECTION2">
<span class="sig-name descname"><span class="n"><span class="pre">Py_END_CRITICAL_SECTION2</span></span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_END_CRITICAL_SECTION2" title="Link to this definition">¶</a><br /></dt>
<dd><p>Ends the critical section and releases the per-object locks.</p>
<p>In the free-threaded build, this macro expands to:</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="w"> </span><span class="n">PyCriticalSection2_End</span><span class="p">(</span><span class="o">&</span><span class="n">_py_cs2</span><span class="p">);</span>
<span class="p">}</span>
</pre></div>
</div>
<p>In the default build, this macro expands to <code class="docutils literal notranslate"><span class="pre">}</span></code>.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.13.</span></p>
</div>
</dd></dl>
</section>
</section>
</section>
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<h3><a href="../contents.html">Table of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">Initialization, Finalization, and Threads</a><ul>
<li><a class="reference internal" href="#before-python-initialization">Before Python Initialization</a></li>
<li><a class="reference internal" href="#global-configuration-variables">Global configuration variables</a></li>
<li><a class="reference internal" href="#initializing-and-finalizing-the-interpreter">Initializing and finalizing the interpreter</a></li>
<li><a class="reference internal" href="#process-wide-parameters">Process-wide parameters</a></li>
<li><a class="reference internal" href="#thread-state-and-the-global-interpreter-lock">Thread State and the Global Interpreter Lock</a><ul>
<li><a class="reference internal" href="#detaching-the-thread-state-from-extension-code">Detaching the thread state from extension code</a></li>
<li><a class="reference internal" href="#non-python-created-threads">Non-Python created threads</a></li>
<li><a class="reference internal" href="#supporting-subinterpreters-in-non-python-threads">Supporting subinterpreters in non-Python threads</a></li>
<li><a class="reference internal" href="#cautions-about-fork">Cautions about fork()</a></li>
<li><a class="reference internal" href="#cautions-regarding-runtime-finalization">Cautions regarding runtime finalization</a></li>
<li><a class="reference internal" href="#high-level-api">High-level API</a></li>
<li><a class="reference internal" href="#low-level-api">Low-level API</a></li>
</ul>
</li>
<li><a class="reference internal" href="#sub-interpreter-support">Sub-interpreter support</a><ul>
<li><a class="reference internal" href="#a-per-interpreter-gil">A Per-Interpreter GIL</a></li>
<li><a class="reference internal" href="#bugs-and-caveats">Bugs and caveats</a></li>
</ul>
</li>
<li><a class="reference internal" href="#asynchronous-notifications">Asynchronous Notifications</a></li>
<li><a class="reference internal" href="#profiling-and-tracing">Profiling and Tracing</a></li>
<li><a class="reference internal" href="#reference-tracing">Reference tracing</a></li>
<li><a class="reference internal" href="#advanced-debugger-support">Advanced Debugger Support</a></li>
<li><a class="reference internal" href="#thread-local-storage-support">Thread Local Storage Support</a><ul>
<li><a class="reference internal" href="#thread-specific-storage-tss-api">Thread Specific Storage (TSS) API</a><ul>
<li><a class="reference internal" href="#dynamic-allocation">Dynamic Allocation</a></li>
<li><a class="reference internal" href="#methods">Methods</a></li>
</ul>
</li>
<li><a class="reference internal" href="#thread-local-storage-tls-api">Thread Local Storage (TLS) API</a></li>
</ul>
</li>
<li><a class="reference internal" href="#synchronization-primitives">Synchronization Primitives</a><ul>
<li><a class="reference internal" href="#python-critical-section-api">Python Critical Section API</a></li>
</ul>
</li>
</ul>
</li>
</ul>
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title="next chapter">Python Initialization Configuration</a></p>
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