path: root/devdocs/python~3.12/c-api%2Finit.html

 <span id="initialization"></span><h1>Initialization, Finalization, and Threads</h1> <p>See also <a class="reference internal" href="init_config#init-config"><span class="std std-ref">Python Initialization Configuration</span></a>.</p> <section id="before-python-initialization"> <span id="pre-init-safe"></span><h2>Before Python Initialization</h2> <p>In an application embedding Python, the <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code>Py_Initialize()</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>Configuration functions:</p> <ul> <li><a class="reference internal" href="import#c.PyImport_AppendInittab" title="PyImport_AppendInittab"><code>PyImport_AppendInittab()</code></a></li> <li><a class="reference internal" href="import#c.PyImport_ExtendInittab" title="PyImport_ExtendInittab"><code>PyImport_ExtendInittab()</code></a></li> <li><code>PyInitFrozenExtensions()</code></li> <li><a class="reference internal" href="memory#c.PyMem_SetAllocator" title="PyMem_SetAllocator"><code>PyMem_SetAllocator()</code></a></li> <li><a class="reference internal" href="memory#c.PyMem_SetupDebugHooks" title="PyMem_SetupDebugHooks"><code>PyMem_SetupDebugHooks()</code></a></li> <li><a class="reference internal" href="memory#c.PyObject_SetArenaAllocator" title="PyObject_SetArenaAllocator"><code>PyObject_SetArenaAllocator()</code></a></li> <li><a class="reference internal" href="#c.Py_SetPath" title="Py_SetPath"><code>Py_SetPath()</code></a></li> <li><a class="reference internal" href="#c.Py_SetProgramName" title="Py_SetProgramName"><code>Py_SetProgramName()</code></a></li> <li><a class="reference internal" href="#c.Py_SetPythonHome" title="Py_SetPythonHome"><code>Py_SetPythonHome()</code></a></li> <li><a class="reference internal" href="#c.Py_SetStandardStreamEncoding" title="Py_SetStandardStreamEncoding"><code>Py_SetStandardStreamEncoding()</code></a></li> <li><a class="reference internal" href="sys#c.PySys_AddWarnOption" title="PySys_AddWarnOption"><code>PySys_AddWarnOption()</code></a></li> <li><a class="reference internal" href="sys#c.PySys_AddXOption" title="PySys_AddXOption"><code>PySys_AddXOption()</code></a></li> <li><a class="reference internal" href="sys#c.PySys_ResetWarnOptions" title="PySys_ResetWarnOptions"><code>PySys_ResetWarnOptions()</code></a></li> </ul> </li> <li>
<p>Informative functions:</p> <ul> <li><a class="reference internal" href="#c.Py_IsInitialized" title="Py_IsInitialized"><code>Py_IsInitialized()</code></a></li> <li><a class="reference internal" href="memory#c.PyMem_GetAllocator" title="PyMem_GetAllocator"><code>PyMem_GetAllocator()</code></a></li> <li><a class="reference internal" href="memory#c.PyObject_GetArenaAllocator" title="PyObject_GetArenaAllocator"><code>PyObject_GetArenaAllocator()</code></a></li> <li><a class="reference internal" href="#c.Py_GetBuildInfo" title="Py_GetBuildInfo"><code>Py_GetBuildInfo()</code></a></li> <li><a class="reference internal" href="#c.Py_GetCompiler" title="Py_GetCompiler"><code>Py_GetCompiler()</code></a></li> <li><a class="reference internal" href="#c.Py_GetCopyright" title="Py_GetCopyright"><code>Py_GetCopyright()</code></a></li> <li><a class="reference internal" href="#c.Py_GetPlatform" title="Py_GetPlatform"><code>Py_GetPlatform()</code></a></li> <li><a class="reference internal" href="#c.Py_GetVersion" title="Py_GetVersion"><code>Py_GetVersion()</code></a></li> </ul> </li> <li>
<p>Utilities:</p> <ul> <li><a class="reference internal" href="sys#c.Py_DecodeLocale" title="Py_DecodeLocale"><code>Py_DecodeLocale()</code></a></li> </ul> </li> <li>
<p>Memory allocators:</p> <ul> <li><a class="reference internal" href="memory#c.PyMem_RawMalloc" title="PyMem_RawMalloc"><code>PyMem_RawMalloc()</code></a></li> <li><a class="reference internal" href="memory#c.PyMem_RawRealloc" title="PyMem_RawRealloc"><code>PyMem_RawRealloc()</code></a></li> <li><a class="reference internal" href="memory#c.PyMem_RawCalloc" title="PyMem_RawCalloc"><code>PyMem_RawCalloc()</code></a></li> <li><a class="reference internal" href="memory#c.PyMem_RawFree" title="PyMem_RawFree"><code>PyMem_RawFree()</code></a></li> </ul> </li> </ul> <div class="admonition note"> <p class="admonition-title">Note</p> <p>The following functions <strong>should not be called</strong> before <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code>Py_Initialize()</code></a>: <a class="reference internal" href="sys#c.Py_EncodeLocale" title="Py_EncodeLocale"><code>Py_EncodeLocale()</code></a>, <a class="reference internal" href="#c.Py_GetPath" title="Py_GetPath"><code>Py_GetPath()</code></a>, <a class="reference internal" href="#c.Py_GetPrefix" title="Py_GetPrefix"><code>Py_GetPrefix()</code></a>, <a class="reference internal" href="#c.Py_GetExecPrefix" title="Py_GetExecPrefix"><code>Py_GetExecPrefix()</code></a>, <a class="reference internal" href="#c.Py_GetProgramFullPath" title="Py_GetProgramFullPath"><code>Py_GetProgramFullPath()</code></a>, <a class="reference internal" href="#c.Py_GetPythonHome" title="Py_GetPythonHome"><code>Py_GetPythonHome()</code></a>, <a class="reference internal" href="#c.Py_GetProgramName" title="Py_GetProgramName"><code>Py_GetProgramName()</code></a> and <a class="reference internal" href="#c.PyEval_InitThreads" title="PyEval_InitThreads"><code>PyEval_InitThreads()</code></a>.</p> </div> </section> <section id="global-configuration-variables"> <span id="global-conf-vars"></span><h2>Global configuration variables</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#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>-b</code> sets <a class="reference internal" href="#c.Py_BytesWarningFlag" title="Py_BytesWarningFlag"><code>Py_BytesWarningFlag</code></a> to 1 and <code>-bb</code> sets <a class="reference internal" href="#c.Py_BytesWarningFlag" title="Py_BytesWarningFlag"><code>Py_BytesWarningFlag</code></a> to 2.</p> <dl class="c var"> <dt class="sig sig-object c" id="c.Py_BytesWarningFlag">
<code>int Py_BytesWarningFlag</code> </dt> <dd>
<p>This API is kept for backward compatibility: setting <a class="reference internal" href="init_config#c.PyConfig.bytes_warning" title="PyConfig.bytes_warning"><code>PyConfig.bytes_warning</code></a> should be used instead, see <a class="reference internal" href="init_config#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#bytes" title="bytes"><code>bytes</code></a> or <a class="reference internal" href="../library/stdtypes#bytearray" title="bytearray"><code>bytearray</code></a> with <a class="reference internal" href="../library/stdtypes#str" title="str"><code>str</code></a> or <a class="reference internal" href="../library/stdtypes#bytes" title="bytes"><code>bytes</code></a> with <a class="reference internal" href="../library/functions#int" title="int"><code>int</code></a>. Issue an error if greater or equal to <code>2</code>.</p> <p>Set by the <a class="reference internal" href="../using/cmdline#cmdoption-b"><code>-b</code></a> option.</p> <div class="deprecated"> <p><span class="versionmodified deprecated">Deprecated since version 3.12.</span></p> </div> </dd>
</dl> <dl class="c var"> <dt class="sig sig-object c" id="c.Py_DebugFlag">
<code>int Py_DebugFlag</code> </dt> <dd>
<p>This API is kept for backward compatibility: setting <a class="reference internal" href="init_config#c.PyConfig.parser_debug" title="PyConfig.parser_debug"><code>PyConfig.parser_debug</code></a> should be used instead, see <a class="reference internal" href="init_config#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#cmdoption-d"><code>-d</code></a> option and the <span class="target" id="index-0"></span><a class="reference internal" href="../using/cmdline#envvar-PYTHONDEBUG"><code>PYTHONDEBUG</code></a> environment variable.</p> <div class="deprecated"> <p><span class="versionmodified deprecated">Deprecated since version 3.12.</span></p> </div> </dd>
</dl> <dl class="c var"> <dt class="sig sig-object c" id="c.Py_DontWriteBytecodeFlag">
<code>int Py_DontWriteBytecodeFlag</code> </dt> <dd>
<p>This API is kept for backward compatibility: setting <a class="reference internal" href="init_config#c.PyConfig.write_bytecode" title="PyConfig.write_bytecode"><code>PyConfig.write_bytecode</code></a> should be used instead, see <a class="reference internal" href="init_config#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>.pyc</code> files on the import of source modules.</p> <p>Set by the <a class="reference internal" href="../using/cmdline#cmdoption-B"><code>-B</code></a> option and the <span class="target" id="index-1"></span><a class="reference internal" href="../using/cmdline#envvar-PYTHONDONTWRITEBYTECODE"><code>PYTHONDONTWRITEBYTECODE</code></a> environment variable.</p> <div class="deprecated"> <p><span class="versionmodified deprecated">Deprecated since version 3.12.</span></p> </div> </dd>
</dl> <dl class="c var"> <dt class="sig sig-object c" id="c.Py_FrozenFlag">
<code>int Py_FrozenFlag</code> </dt> <dd>
<p>This API is kept for backward compatibility: setting <a class="reference internal" href="init_config#c.PyConfig.pathconfig_warnings" title="PyConfig.pathconfig_warnings"><code>PyConfig.pathconfig_warnings</code></a> should be used instead, see <a class="reference internal" href="init_config#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>Py_GetPath()</code></a>.</p> <p>Private flag used by <code>_freeze_module</code> and <code>frozenmain</code> programs.</p> <div class="deprecated"> <p><span class="versionmodified deprecated">Deprecated since version 3.12.</span></p> </div> </dd>
</dl> <dl class="c var"> <dt class="sig sig-object c" id="c.Py_HashRandomizationFlag">
<code>int Py_HashRandomizationFlag</code> </dt> <dd>
<p>This API is kept for backward compatibility: setting <a class="reference internal" href="init_config#c.PyConfig.hash_seed" title="PyConfig.hash_seed"><code>PyConfig.hash_seed</code></a> and <a class="reference internal" href="init_config#c.PyConfig.use_hash_seed" title="PyConfig.use_hash_seed"><code>PyConfig.use_hash_seed</code></a> should be used instead, see <a class="reference internal" href="init_config#init-config"><span class="std std-ref">Python Initialization Configuration</span></a>.</p> <p>Set to <code>1</code> if the <span class="target" id="index-2"></span><a class="reference internal" href="../using/cmdline#envvar-PYTHONHASHSEED"><code>PYTHONHASHSEED</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#envvar-PYTHONHASHSEED"><code>PYTHONHASHSEED</code></a> environment variable to initialize the secret hash seed.</p> <div class="deprecated"> <p><span class="versionmodified deprecated">Deprecated since version 3.12.</span></p> </div> </dd>
</dl> <dl class="c var"> <dt class="sig sig-object c" id="c.Py_IgnoreEnvironmentFlag">
<code>int Py_IgnoreEnvironmentFlag</code> </dt> <dd>
<p>This API is kept for backward compatibility: setting <a class="reference internal" href="init_config#c.PyConfig.use_environment" title="PyConfig.use_environment"><code>PyConfig.use_environment</code></a> should be used instead, see <a class="reference internal" href="init_config#init-config"><span class="std std-ref">Python Initialization Configuration</span></a>.</p> <p>Ignore all <code>PYTHON*</code> environment variables, e.g. <span class="target" id="index-4"></span><a class="reference internal" href="../using/cmdline#envvar-PYTHONPATH"><code>PYTHONPATH</code></a> and <span class="target" id="index-5"></span><a class="reference internal" href="../using/cmdline#envvar-PYTHONHOME"><code>PYTHONHOME</code></a>, that might be set.</p> <p>Set by the <a class="reference internal" href="../using/cmdline#cmdoption-E"><code>-E</code></a> and <a class="reference internal" href="../using/cmdline#cmdoption-I"><code>-I</code></a> options.</p> <div class="deprecated"> <p><span class="versionmodified deprecated">Deprecated since version 3.12.</span></p> </div> </dd>
</dl> <dl class="c var"> <dt class="sig sig-object c" id="c.Py_InspectFlag">
<code>int Py_InspectFlag</code> </dt> <dd>
<p>This API is kept for backward compatibility: setting <a class="reference internal" href="init_config#c.PyConfig.inspect" title="PyConfig.inspect"><code>PyConfig.inspect</code></a> should be used instead, see <a class="reference internal" href="init_config#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#cmdoption-c"><code>-c</code></a> option is used, enter interactive mode after executing the script or the command, even when <a class="reference internal" href="../library/sys#sys.stdin" title="sys.stdin"><code>sys.stdin</code></a> does not appear to be a terminal.</p> <p>Set by the <a class="reference internal" href="../using/cmdline#cmdoption-i"><code>-i</code></a> option and the <span class="target" id="index-6"></span><a class="reference internal" href="../using/cmdline#envvar-PYTHONINSPECT"><code>PYTHONINSPECT</code></a> environment variable.</p> <div class="deprecated"> <p><span class="versionmodified deprecated">Deprecated since version 3.12.</span></p> </div> </dd>
</dl> <dl class="c var"> <dt class="sig sig-object c" id="c.Py_InteractiveFlag">
<code>int Py_InteractiveFlag</code> </dt> <dd>
<p>This API is kept for backward compatibility: setting <a class="reference internal" href="init_config#c.PyConfig.interactive" title="PyConfig.interactive"><code>PyConfig.interactive</code></a> should be used instead, see <a class="reference internal" href="init_config#init-config"><span class="std std-ref">Python Initialization Configuration</span></a>.</p> <p>Set by the <a class="reference internal" href="../using/cmdline#cmdoption-i"><code>-i</code></a> option.</p> <div class="deprecated"> <p><span class="versionmodified deprecated">Deprecated since version 3.12.</span></p> </div> </dd>
</dl> <dl class="c var"> <dt class="sig sig-object c" id="c.Py_IsolatedFlag">
<code>int Py_IsolatedFlag</code> </dt> <dd>
<p>This API is kept for backward compatibility: setting <a class="reference internal" href="init_config#c.PyConfig.isolated" title="PyConfig.isolated"><code>PyConfig.isolated</code></a> should be used instead, see <a class="reference internal" href="init_config#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#sys.path" title="sys.path"><code>sys.path</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#cmdoption-I"><code>-I</code></a> option.</p> <div class="versionadded"> <p><span class="versionmodified added">New in version 3.4.</span></p> </div> <div class="deprecated"> <p><span class="versionmodified deprecated">Deprecated since version 3.12.</span></p> </div> </dd>
</dl> <dl class="c var"> <dt class="sig sig-object c" id="c.Py_LegacyWindowsFSEncodingFlag">
<code>int Py_LegacyWindowsFSEncodingFlag</code> </dt> <dd>
<p>This API is kept for backward compatibility: setting <a class="reference internal" href="init_config#c.PyPreConfig.legacy_windows_fs_encoding" title="PyPreConfig.legacy_windows_fs_encoding"><code>PyPreConfig.legacy_windows_fs_encoding</code></a> should be used instead, see <a class="reference internal" href="init_config#init-config"><span class="std std-ref">Python Initialization Configuration</span></a>.</p> <p>If the flag is non-zero, use the <code>mbcs</code> encoding with <code>replace</code> error handler, instead of the UTF-8 encoding with <code>surrogatepass</code> error handler, for the <a class="reference internal" href="../glossary#term-filesystem-encoding-and-error-handler"><span class="xref std std-term">filesystem encoding and error handler</span></a>.</p> <p>Set to <code>1</code> if the <span class="target" id="index-7"></span><a class="reference internal" href="../using/cmdline#envvar-PYTHONLEGACYWINDOWSFSENCODING"><code>PYTHONLEGACYWINDOWSFSENCODING</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="https://docs.python.org/3.12/library/intro.html#availability"><span class="std std-ref">Availability</span></a>: Windows.</p> </div> <div class="deprecated"> <p><span class="versionmodified deprecated">Deprecated since version 3.12.</span></p> </div> </dd>
</dl> <dl class="c var"> <dt class="sig sig-object c" id="c.Py_LegacyWindowsStdioFlag">
<code>int Py_LegacyWindowsStdioFlag</code> </dt> <dd>
<p>This API is kept for backward compatibility: setting <a class="reference internal" href="init_config#c.PyConfig.legacy_windows_stdio" title="PyConfig.legacy_windows_stdio"><code>PyConfig.legacy_windows_stdio</code></a> should be used instead, see <a class="reference internal" href="init_config#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#io.FileIO" title="io.FileIO"><code>io.FileIO</code></a> instead of <code>io._WindowsConsoleIO</code> for <a class="reference internal" href="../library/sys#module-sys" title="sys: Access system-specific parameters and functions."><code>sys</code></a> standard streams.</p> <p>Set to <code>1</code> if the <span class="target" id="index-9"></span><a class="reference internal" href="../using/cmdline#envvar-PYTHONLEGACYWINDOWSSTDIO"><code>PYTHONLEGACYWINDOWSSTDIO</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="https://docs.python.org/3.12/library/intro.html#availability"><span class="std std-ref">Availability</span></a>: Windows.</p> </div> <div class="deprecated"> <p><span class="versionmodified deprecated">Deprecated since version 3.12.</span></p> </div> </dd>
</dl> <dl class="c var"> <dt class="sig sig-object c" id="c.Py_NoSiteFlag">
<code>int Py_NoSiteFlag</code> </dt> <dd>
<p>This API is kept for backward compatibility: setting <a class="reference internal" href="init_config#c.PyConfig.site_import" title="PyConfig.site_import"><code>PyConfig.site_import</code></a> should be used instead, see <a class="reference internal" href="init_config#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#module-site" title="site: Module responsible for site-specific configuration."><code>site</code></a> and the site-dependent manipulations of <a class="reference internal" href="../library/sys#sys.path" title="sys.path"><code>sys.path</code></a> that it entails. Also disable these manipulations if <a class="reference internal" href="../library/site#module-site" title="site: Module responsible for site-specific configuration."><code>site</code></a> is explicitly imported later (call <a class="reference internal" href="../library/site#site.main" title="site.main"><code>site.main()</code></a> if you want them to be triggered).</p> <p>Set by the <a class="reference internal" href="../using/cmdline#cmdoption-S"><code>-S</code></a> option.</p> <div class="deprecated"> <p><span class="versionmodified deprecated">Deprecated since version 3.12.</span></p> </div> </dd>
</dl> <dl class="c var"> <dt class="sig sig-object c" id="c.Py_NoUserSiteDirectory">
<code>int Py_NoUserSiteDirectory</code> </dt> <dd>
<p>This API is kept for backward compatibility: setting <a class="reference internal" href="init_config#c.PyConfig.user_site_directory" title="PyConfig.user_site_directory"><code>PyConfig.user_site_directory</code></a> should be used instead, see <a class="reference internal" href="init_config#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#site.USER_SITE" title="site.USER_SITE"><code>user site-packages directory</code></a> to <a class="reference internal" href="../library/sys#sys.path" title="sys.path"><code>sys.path</code></a>.</p> <p>Set by the <a class="reference internal" href="../using/cmdline#cmdoption-s"><code>-s</code></a> and <a class="reference internal" href="../using/cmdline#cmdoption-I"><code>-I</code></a> options, and the <span class="target" id="index-11"></span><a class="reference internal" href="../using/cmdline#envvar-PYTHONNOUSERSITE"><code>PYTHONNOUSERSITE</code></a> environment variable.</p> <div class="deprecated"> <p><span class="versionmodified deprecated">Deprecated since version 3.12.</span></p> </div> </dd>
</dl> <dl class="c var"> <dt class="sig sig-object c" id="c.Py_OptimizeFlag">
<code>int Py_OptimizeFlag</code> </dt> <dd>
<p>This API is kept for backward compatibility: setting <a class="reference internal" href="init_config#c.PyConfig.optimization_level" title="PyConfig.optimization_level"><code>PyConfig.optimization_level</code></a> should be used instead, see <a class="reference internal" href="init_config#init-config"><span class="std std-ref">Python Initialization Configuration</span></a>.</p> <p>Set by the <a class="reference internal" href="../using/cmdline#cmdoption-O"><code>-O</code></a> option and the <span class="target" id="index-12"></span><a class="reference internal" href="../using/cmdline#envvar-PYTHONOPTIMIZE"><code>PYTHONOPTIMIZE</code></a> environment variable.</p> <div class="deprecated"> <p><span class="versionmodified deprecated">Deprecated since version 3.12.</span></p> </div> </dd>
</dl> <dl class="c var"> <dt class="sig sig-object c" id="c.Py_QuietFlag">
<code>int Py_QuietFlag</code> </dt> <dd>
<p>This API is kept for backward compatibility: setting <a class="reference internal" href="init_config#c.PyConfig.quiet" title="PyConfig.quiet"><code>PyConfig.quiet</code></a> should be used instead, see <a class="reference internal" href="init_config#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#cmdoption-q"><code>-q</code></a> option.</p> <div class="versionadded"> <p><span class="versionmodified added">New in version 3.2.</span></p> </div> <div class="deprecated"> <p><span class="versionmodified deprecated">Deprecated since version 3.12.</span></p> </div> </dd>
</dl> <dl class="c var"> <dt class="sig sig-object c" id="c.Py_UnbufferedStdioFlag">
<code>int Py_UnbufferedStdioFlag</code> </dt> <dd>
<p>This API is kept for backward compatibility: setting <a class="reference internal" href="init_config#c.PyConfig.buffered_stdio" title="PyConfig.buffered_stdio"><code>PyConfig.buffered_stdio</code></a> should be used instead, see <a class="reference internal" href="init_config#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#cmdoption-u"><code>-u</code></a> option and the <span class="target" id="index-13"></span><a class="reference internal" href="../using/cmdline#envvar-PYTHONUNBUFFERED"><code>PYTHONUNBUFFERED</code></a> environment variable.</p> <div class="deprecated"> <p><span class="versionmodified deprecated">Deprecated since version 3.12.</span></p> </div> </dd>
</dl> <dl class="c var"> <dt class="sig sig-object c" id="c.Py_VerboseFlag">
<code>int Py_VerboseFlag</code> </dt> <dd>
<p>This API is kept for backward compatibility: setting <a class="reference internal" href="init_config#c.PyConfig.verbose" title="PyConfig.verbose"><code>PyConfig.verbose</code></a> should be used instead, see <a class="reference internal" href="init_config#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>2</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#cmdoption-1"><code>-v</code></a> option and the <span class="target" id="index-14"></span><a class="reference internal" href="../using/cmdline#envvar-PYTHONVERBOSE"><code>PYTHONVERBOSE</code></a> environment variable.</p> <div class="deprecated"> <p><span class="versionmodified deprecated">Deprecated since version 3.12.</span></p> </div> </dd>
</dl> </section> <section id="initializing-and-finalizing-the-interpreter"> <h2>Initializing and finalizing the interpreter</h2> <dl class="c function"> <dt class="sig sig-object c" id="c.Py_Initialize">
<code>void Py_Initialize()</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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>sys.modules</code>), and creates the fundamental modules <a class="reference internal" href="../library/builtins#module-builtins" title="builtins: The module that provides the built-in namespace."><code>builtins</code></a>, <a class="reference internal" href="../library/__main__#module-__main__" title="__main__: The environment where top-level code is run. Covers command-line interfaces, import-time behavior, and ``__name__ == '__main__'``."><code>__main__</code></a> and <a class="reference internal" href="../library/sys#module-sys" title="sys: Access system-specific parameters and functions."><code>sys</code></a>. It also initializes the module search path (<code>sys.path</code>). It does not set <code>sys.argv</code>; use <a class="reference internal" href="#c.PySys_SetArgvEx" title="PySys_SetArgvEx"><code>PySys_SetArgvEx()</code></a> 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>Py_FinalizeEx()</code></a> first). There is no return value; it is a fatal error if the initialization fails.</p> <p>Use the <a class="reference internal" href="init_config#c.Py_InitializeFromConfig" title="Py_InitializeFromConfig"><code>Py_InitializeFromConfig()</code></a> function to customize the <a class="reference internal" href="init_config#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>O_TEXT</code> to <code>O_BINARY</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">
<code>void Py_InitializeEx(int initsigs)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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>Py_Initialize()</code></a> if <em>initsigs</em> is <code>1</code>. If <em>initsigs</em> is <code>0</code>, it skips initialization registration of signal handlers, which might be useful when Python is embedded.</p> <p>Use the <a class="reference internal" href="init_config#c.Py_InitializeFromConfig" title="Py_InitializeFromConfig"><code>Py_InitializeFromConfig()</code></a> function to customize the <a class="reference internal" href="init_config#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_IsInitialized">
<code>int Py_IsInitialized()</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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>Py_FinalizeEx()</code></a> is called, this returns false until <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code>Py_Initialize()</code></a> is called again.</p> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.Py_FinalizeEx">
<code>int Py_FinalizeEx()</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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>Py_Initialize()</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>Py_NewInterpreter()</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>Py_Initialize()</code></a>. Ideally, this frees all memory allocated by the Python interpreter. 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>Py_Initialize()</code></a> again first). Normally the return value is <code>0</code>. If there were errors during finalization (flushing buffered data), <code>-1</code> is returned.</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#object.__del__" title="object.__del__"><code>__del__()</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. 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>Py_Initialize()</code></a> and <a class="reference internal" href="#c.Py_FinalizeEx" title="Py_FinalizeEx"><code>Py_FinalizeEx()</code></a> more than once.</p> <p class="audit-hook">Raises an <a class="reference internal" href="../library/sys#auditing"><span class="std std-ref">auditing event</span></a> <code>cpython._PySys_ClearAuditHooks</code> with no arguments.</p> <div class="versionadded"> <p><span class="versionmodified added">New in version 3.6.</span></p> </div> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.Py_Finalize">
<code>void Py_Finalize()</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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>Py_FinalizeEx()</code></a> that disregards the return value.</p> </dd>
</dl> </section> <section id="process-wide-parameters"> <h2>Process-wide parameters</h2> <dl class="c function"> <dt class="sig sig-object c" id="c.Py_SetStandardStreamEncoding">
<code>int Py_SetStandardStreamEncoding(const char *encoding, const char *errors)</code> </dt> <dd>
<p id="index-16">This API is kept for backward compatibility: setting <a class="reference internal" href="init_config#c.PyConfig.stdio_encoding" title="PyConfig.stdio_encoding"><code>PyConfig.stdio_encoding</code></a> and <a class="reference internal" href="init_config#c.PyConfig.stdio_errors" title="PyConfig.stdio_errors"><code>PyConfig.stdio_errors</code></a> should be used instead, see <a class="reference internal" href="init_config#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>Py_Initialize()</code></a>, if it is called at all. It specifies which encoding and error handling to use with standard IO, with the same meanings as in <a class="reference internal" href="../library/stdtypes#str.encode" title="str.encode"><code>str.encode()</code></a>.</p> <p>It overrides <span class="target" id="index-17"></span><a class="reference internal" href="../using/cmdline#envvar-PYTHONIOENCODING"><code>PYTHONIOENCODING</code></a> values, and allows embedding code to control IO encoding when the environment variable does not work.</p> <p><em>encoding</em> and/or <em>errors</em> may be <code>NULL</code> to use <span class="target" id="index-18"></span><a class="reference internal" href="../using/cmdline#envvar-PYTHONIOENCODING"><code>PYTHONIOENCODING</code></a> and/or default values (depending on other settings).</p> <p>Note that <a class="reference internal" href="../library/sys#sys.stderr" title="sys.stderr"><code>sys.stderr</code></a> always uses the “backslashreplace” error handler, regardless of this (or any other) setting.</p> <p>If <a class="reference internal" href="#c.Py_FinalizeEx" title="Py_FinalizeEx"><code>Py_FinalizeEx()</code></a> is called, this function will need to be called again in order to affect subsequent calls to <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code>Py_Initialize()</code></a>.</p> <p>Returns <code>0</code> if successful, a nonzero value on error (e.g. calling after the interpreter has already been initialized).</p> <div class="versionadded"> <p><span class="versionmodified added">New in version 3.4.</span></p> </div> <div class="deprecated"> <p><span class="versionmodified deprecated">Deprecated since version 3.11.</span></p> </div> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.Py_SetProgramName">
<code>void Py_SetProgramName(const wchar_t *name)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p id="index-19">This API is kept for backward compatibility: setting <a class="reference internal" href="init_config#c.PyConfig.program_name" title="PyConfig.program_name"><code>PyConfig.program_name</code></a> should be used instead, see <a class="reference internal" href="init_config#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>Py_Initialize()</code></a> is called for the first time, if it is called at all. It tells the interpreter the value of the <code>argv[0]</code> argument to the <code>main()</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>Py_GetPath()</code></a> and some other functions below to find the Python run-time libraries relative to the interpreter executable. The default value is <code>'python'</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#c.Py_DecodeLocale" title="Py_DecodeLocale"><code>Py_DecodeLocale()</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"> <p><span class="versionmodified deprecated">Deprecated since version 3.11.</span></p> </div> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.Py_GetProgramName">
<code>wchar_t *Py_GetProgramName()</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p id="index-20">Return the program name set with <a class="reference internal" href="#c.Py_SetProgramName" title="Py_SetProgramName"><code>Py_SetProgramName()</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>Py_Initialize()</code></a>, otherwise it returns <code>NULL</code>.</p> <div class="versionchanged"> <p><span class="versionmodified changed">Changed in version 3.10: </span>It now returns <code>NULL</code> if called before <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code>Py_Initialize()</code></a>.</p> </div> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.Py_GetPrefix">
<code>wchar_t *Py_GetPrefix()</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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="#c.Py_SetProgramName" title="Py_SetProgramName"><code>Py_SetProgramName()</code></a> and some environment variables; for example, if the program name is <code>'/usr/local/bin/python'</code>, the prefix is <code>'/usr/local'</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>Makefile</code> and the <a class="reference internal" href="../using/configure#cmdoption-prefix"><code>--prefix</code></a> argument to the <strong class="program">configure</strong> script at build time. The value is available to Python code as <code>sys.prefix</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>Py_Initialize()</code></a>, otherwise it returns <code>NULL</code>.</p> <div class="versionchanged"> <p><span class="versionmodified changed">Changed in version 3.10: </span>It now returns <code>NULL</code> if called before <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code>Py_Initialize()</code></a>.</p> </div> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.Py_GetExecPrefix">
<code>wchar_t *Py_GetExecPrefix()</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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="#c.Py_SetProgramName" title="Py_SetProgramName"><code>Py_SetProgramName()</code></a> and some environment variables; for example, if the program name is <code>'/usr/local/bin/python'</code>, the exec-prefix is <code>'/usr/local'</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>Makefile</code> and the <code>--exec-prefix</code> argument to the <strong class="program">configure</strong> script at build time. The value is available to Python code as <code>sys.exec_prefix</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>/usr/local/plat</code> subtree while platform independent may be installed in <code>/usr/local</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>/usr/local</code> between platforms while having <code>/usr/local/plat</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>Py_Initialize()</code></a>, otherwise it returns <code>NULL</code>.</p> <div class="versionchanged"> <p><span class="versionmodified changed">Changed in version 3.10: </span>It now returns <code>NULL</code> if called before <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code>Py_Initialize()</code></a>.</p> </div> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.Py_GetProgramFullPath">
<code>wchar_t *Py_GetProgramFullPath()</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p id="index-21">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="#c.Py_SetProgramName" title="Py_SetProgramName"><code>Py_SetProgramName()</code></a> above). The returned string points into static storage; the caller should not modify its value. The value is available to Python code as <code>sys.executable</code>.</p> <p>This function should not be called before <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code>Py_Initialize()</code></a>, otherwise it returns <code>NULL</code>.</p> <div class="versionchanged"> <p><span class="versionmodified changed">Changed in version 3.10: </span>It now returns <code>NULL</code> if called before <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code>Py_Initialize()</code></a>.</p> </div> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.Py_GetPath">
<code>wchar_t *Py_GetPath()</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p id="index-22">Return the default module search path; this is computed from the program name (set by <a class="reference internal" href="#c.Py_SetProgramName" title="Py_SetProgramName"><code>Py_SetProgramName()</code></a> above) 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>':'</code> on Unix and macOS, <code>';'</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#sys.path" title="sys.path"><code>sys.path</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>Py_Initialize()</code></a>, otherwise it returns <code>NULL</code>.</p> <div class="versionchanged"> <p><span class="versionmodified changed">Changed in version 3.10: </span>It now returns <code>NULL</code> if called before <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code>Py_Initialize()</code></a>.</p> </div> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.Py_SetPath">
<code>void Py_SetPath(const wchar_t*)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.7.</em><p id="index-23">This API is kept for backward compatibility: setting <a class="reference internal" href="init_config#c.PyConfig.module_search_paths" title="PyConfig.module_search_paths"><code>PyConfig.module_search_paths</code></a> and <a class="reference internal" href="init_config#c.PyConfig.module_search_paths_set" title="PyConfig.module_search_paths_set"><code>PyConfig.module_search_paths_set</code></a> should be used instead, see <a class="reference internal" href="init_config#init-config"><span class="std std-ref">Python Initialization Configuration</span></a>.</p> <p>Set the default module search path. If this function is called before <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code>Py_Initialize()</code></a>, then <a class="reference internal" href="#c.Py_GetPath" title="Py_GetPath"><code>Py_GetPath()</code></a> won’t attempt to compute a default search path but uses the one provided instead. This is useful if Python is embedded by an application that has full knowledge of the location of all modules. The path components should be separated by the platform dependent delimiter character, which is <code>':'</code> on Unix and macOS, <code>';'</code> on Windows.</p> <p>This also causes <a class="reference internal" href="../library/sys#sys.executable" title="sys.executable"><code>sys.executable</code></a> to be set to the program full path (see <a class="reference internal" href="#c.Py_GetProgramFullPath" title="Py_GetProgramFullPath"><code>Py_GetProgramFullPath()</code></a>) and for <a class="reference internal" href="../library/sys#sys.prefix" title="sys.prefix"><code>sys.prefix</code></a> and <a class="reference internal" href="../library/sys#sys.exec_prefix" title="sys.exec_prefix"><code>sys.exec_prefix</code></a> to be empty. It is up to the caller to modify these if required after calling <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code>Py_Initialize()</code></a>.</p> <p>Use <a class="reference internal" href="sys#c.Py_DecodeLocale" title="Py_DecodeLocale"><code>Py_DecodeLocale()</code></a> to decode a bytes string to get a <span class="c-expr sig sig-inline c"><span class="n">wchar_</span><span class="p">*</span></span> string.</p> <p>The path argument is copied internally, so the caller may free it after the call completes.</p> <div class="versionchanged"> <p><span class="versionmodified changed">Changed in version 3.8: </span>The program full path is now used for <a class="reference internal" href="../library/sys#sys.executable" title="sys.executable"><code>sys.executable</code></a>, instead of the program name.</p> </div> <div class="deprecated"> <p><span class="versionmodified deprecated">Deprecated since version 3.11.</span></p> </div> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.Py_GetVersion">
<code>const char *Py_GetVersion()</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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> <pre data-language="c">"3.0a5+ (py3k:63103M, May 12 2008, 00:53:55) \n[GCC 4.2.3]"
</pre> <p id="index-24">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#sys.version" title="sys.version"><code>sys.version</code></a>.</p> <p>See also the <a class="reference internal" href="apiabiversion#c.Py_Version" title="Py_Version"><code>Py_Version</code></a> constant.</p> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.Py_GetPlatform">
<code>const char *Py_GetPlatform()</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p id="index-25">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>'sunos5'</code>. On macOS, it is <code>'darwin'</code>. On Windows, it is <code>'win'</code>. The returned string points into static storage; the caller should not modify its value. The value is available to Python code as <code>sys.platform</code>.</p> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.Py_GetCopyright">
<code>const char *Py_GetCopyright()</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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>'Copyright 1991-1995 Stichting Mathematisch Centrum, Amsterdam'</code></p> <p id="index-26">The returned string points into static storage; the caller should not modify its value. The value is available to Python code as <code>sys.copyright</code>.</p> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.Py_GetCompiler">
<code>const char *Py_GetCompiler()</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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> <pre data-language="c">"[GCC 2.7.2.2]"
</pre> <p id="index-27">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>sys.version</code>.</p> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.Py_GetBuildInfo">
<code>const char *Py_GetBuildInfo()</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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> <pre data-language="c">"#67, Aug  1 1997, 22:34:28"
</pre> <p id="index-28">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>sys.version</code>.</p> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PySys_SetArgvEx">
<code>void PySys_SetArgvEx(int argc, wchar_t **argv, int updatepath)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p id="index-29">This API is kept for backward compatibility: setting <a class="reference internal" href="init_config#c.PyConfig.argv" title="PyConfig.argv"><code>PyConfig.argv</code></a>, <a class="reference internal" href="init_config#c.PyConfig.parse_argv" title="PyConfig.parse_argv"><code>PyConfig.parse_argv</code></a> and <a class="reference internal" href="init_config#c.PyConfig.safe_path" title="PyConfig.safe_path"><code>PyConfig.safe_path</code></a> should be used instead, see <a class="reference internal" href="init_config#init-config"><span class="std std-ref">Python Initialization Configuration</span></a>.</p> <p>Set <a class="reference internal" href="../library/sys#sys.argv" title="sys.argv"><code>sys.argv</code></a> based on <em>argc</em> and <em>argv</em>. These parameters are similar to those passed to the program’s <code>main()</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#sys.argv" title="sys.argv"><code>sys.argv</code></a>, a fatal condition is signalled using <a class="reference internal" href="sys#c.Py_FatalError" title="Py_FatalError"><code>Py_FatalError()</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#sys.path" title="sys.path"><code>sys.path</code></a> according to the following algorithm:</p> <ul class="simple"> <li>If the name of an existing script is passed in <code>argv[0]</code>, the absolute path of the directory where the script is located is prepended to <a class="reference internal" href="../library/sys#sys.path" title="sys.path"><code>sys.path</code></a>.</li> <li>Otherwise (that is, if <em>argc</em> is <code>0</code> or <code>argv[0]</code> doesn’t point to an existing file name), an empty string is prepended to <a class="reference internal" href="../library/sys#sys.path" title="sys.path"><code>sys.path</code></a>, which is the same as prepending the current working directory (<code>"."</code>).</li> </ul> <p>Use <a class="reference internal" href="sys#c.Py_DecodeLocale" title="Py_DecodeLocale"><code>Py_DecodeLocale()</code></a> to decode a bytes string to get a <span class="c-expr sig sig-inline c"><span class="n">wchar_</span><span class="p">*</span></span> string.</p> <p>See also <a class="reference internal" href="init_config#c.PyConfig.orig_argv" title="PyConfig.orig_argv"><code>PyConfig.orig_argv</code></a> and <a class="reference internal" href="init_config#c.PyConfig.argv" title="PyConfig.argv"><code>PyConfig.argv</code></a> members of the <a class="reference internal" href="init_config#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>0</code> as <em>updatepath</em>, and update <a class="reference internal" href="../library/sys#sys.path" title="sys.path"><code>sys.path</code></a> themselves if desired. See <a class="reference external" href="https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-5983">CVE-2008-5983</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#sys.path" title="sys.path"><code>sys.path</code></a> element after having called <a class="reference internal" href="#c.PySys_SetArgv" title="PySys_SetArgv"><code>PySys_SetArgv()</code></a>, for example using:</p> <pre data-language="c">PyRun_SimpleString("import sys; sys.path.pop(0)\n");
</pre> </div> <div class="versionadded"> <p><span class="versionmodified added">New in version 3.1.3.</span></p> </div> <div class="deprecated"> <p><span class="versionmodified deprecated">Deprecated since version 3.11.</span></p> </div> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PySys_SetArgv">
<code>void PySys_SetArgv(int argc, wchar_t **argv)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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#c.PyConfig.argv" title="PyConfig.argv"><code>PyConfig.argv</code></a> and <a class="reference internal" href="init_config#c.PyConfig.parse_argv" title="PyConfig.parse_argv"><code>PyConfig.parse_argv</code></a> should be used instead, see <a class="reference internal" href="init_config#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>PySys_SetArgvEx()</code></a> with <em>updatepath</em> set to <code>1</code> unless the <strong class="program">python</strong> interpreter was started with the <a class="reference internal" href="../using/cmdline#cmdoption-I"><code>-I</code></a>.</p> <p>Use <a class="reference internal" href="sys#c.Py_DecodeLocale" title="Py_DecodeLocale"><code>Py_DecodeLocale()</code></a> to decode a bytes string to get a <span class="c-expr sig sig-inline c"><span class="n">wchar_</span><span class="p">*</span></span> string.</p> <p>See also <a class="reference internal" href="init_config#c.PyConfig.orig_argv" title="PyConfig.orig_argv"><code>PyConfig.orig_argv</code></a> and <a class="reference internal" href="init_config#c.PyConfig.argv" title="PyConfig.argv"><code>PyConfig.argv</code></a> members of the <a class="reference internal" href="init_config#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#cmdoption-I"><code>-I</code></a>.</p> </div> <div class="deprecated"> <p><span class="versionmodified deprecated">Deprecated since version 3.11.</span></p> </div> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.Py_SetPythonHome">
<code>void Py_SetPythonHome(const wchar_t *home)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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#c.PyConfig.home" title="PyConfig.home"><code>PyConfig.home</code></a> should be used instead, see <a class="reference internal" href="init_config#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-30"></span><a class="reference internal" href="../using/cmdline#envvar-PYTHONHOME"><code>PYTHONHOME</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#c.Py_DecodeLocale" title="Py_DecodeLocale"><code>Py_DecodeLocale()</code></a> to decode a bytes string to get a <span class="c-expr sig sig-inline c"><span class="n">wchar_</span><span class="p">*</span></span> string.</p> <div class="deprecated"> <p><span class="versionmodified deprecated">Deprecated since version 3.11.</span></p> </div> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.Py_GetPythonHome">
<code>wchar_t *Py_GetPythonHome()</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Return the default “home”, that is, the value set by a previous call to <a class="reference internal" href="#c.Py_SetPythonHome" title="Py_SetPythonHome"><code>Py_SetPythonHome()</code></a>, or the value of the <span class="target" id="index-31"></span><a class="reference internal" href="../using/cmdline#envvar-PYTHONHOME"><code>PYTHONHOME</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>Py_Initialize()</code></a>, otherwise it returns <code>NULL</code>.</p> <div class="versionchanged"> <p><span class="versionmodified changed">Changed in version 3.10: </span>It now returns <code>NULL</code> if called before <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code>Py_Initialize()</code></a>.</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</h2> <p id="index-32">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#term-global-interpreter-lock"><span class="xref std std-term">global interpreter lock</span></a> or <a class="reference internal" href="../glossary#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-33">Therefore, the rule exists that only the thread that has acquired the <a class="reference internal" href="../glossary#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#sys.setswitchinterval" title="sys.setswitchinterval"><code>sys.setswitchinterval()</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-34">The Python interpreter keeps some thread-specific bookkeeping information inside a data structure called <a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><code>PyThreadState</code></a>. There’s also one global variable pointing to the current <a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><code>PyThreadState</code></a>: it can be retrieved using <a class="reference internal" href="#c.PyThreadState_Get" title="PyThreadState_Get"><code>PyThreadState_Get()</code></a>.</p> <section id="releasing-the-gil-from-extension-code"> <h3>Releasing the GIL from extension code</h3> <p>Most extension code manipulating the <a class="reference internal" href="../glossary#term-GIL"><span class="xref std std-term">GIL</span></a> has the following simple structure:</p> <pre data-language="c">Save the thread state in a local variable.
Release the global interpreter lock.
... Do some blocking I/O operation ...
Reacquire the global interpreter lock.
Restore the thread state from the local variable.
</pre> <p>This is so common that a pair of macros exists to simplify it:</p> <pre data-language="c">Py_BEGIN_ALLOW_THREADS
... Do some blocking I/O operation ...
Py_END_ALLOW_THREADS
</pre> <p id="index-35">The <a class="reference internal" href="#c.Py_BEGIN_ALLOW_THREADS" title="Py_BEGIN_ALLOW_THREADS"><code>Py_BEGIN_ALLOW_THREADS</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>Py_END_ALLOW_THREADS</code></a> macro closes the block.</p> <p>The block above expands to the following code:</p> <pre data-language="c">PyThreadState *_save;

_save = PyEval_SaveThread();
... Do some blocking I/O operation ...
PyEval_RestoreThread(_save);
</pre> <p id="index-36">Here is how these functions work: the global interpreter lock is used to protect the pointer to the current thread state. When releasing the lock and saving the thread state, the current thread state pointer must be retrieved before the lock is released (since another thread could immediately acquire the lock and store its own thread state in the global variable). Conversely, when acquiring the lock and restoring the thread state, the lock must be acquired before storing the thread state pointer.</p> <div class="admonition note"> <p class="admonition-title">Note</p> <p>Calling system I/O functions is the most common use case for releasing the GIL, 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#module-zlib" title="zlib: Low-level interface to compression and decompression routines compatible with gzip."><code>zlib</code></a> and <a class="reference internal" href="../library/hashlib#module-hashlib" title="hashlib: Secure hash and message digest algorithms."><code>hashlib</code></a> modules release the GIL when compressing or hashing data.</p> </div> </section> <section id="non-python-created-threads"> <span id="gilstate"></span><h3>Non-Python created threads</h3> <p>When threads are created using the dedicated Python APIs (such as the <a class="reference internal" href="../library/threading#module-threading" title="threading: Thread-based parallelism."><code>threading</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 GIL, nor is there a thread state structure for them.</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 a thread state data structure, then acquiring the GIL, and finally storing their thread state pointer, before you can start using the Python/C API. When you are done, you should reset the thread state pointer, release the GIL, and finally free the thread state data structure.</p> <p>The <a class="reference internal" href="#c.PyGILState_Ensure" title="PyGILState_Ensure"><code>PyGILState_Ensure()</code></a> and <a class="reference internal" href="#c.PyGILState_Release" title="PyGILState_Release"><code>PyGILState_Release()</code></a> functions do all of the above automatically. The typical idiom for calling into Python from a C thread is:</p> <pre data-language="c">PyGILState_STATE gstate;
gstate = PyGILState_Ensure();

/* Perform Python actions here. */
result = CallSomeFunction();
/* evaluate result or handle exception */

/* Release the thread. No Python API allowed beyond this point. */
PyGILState_Release(gstate);
</pre> <p>Note that the <code>PyGILState_*</code> functions assume there is only one global interpreter (created automatically by <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code>Py_Initialize()</code></a>). Python supports the creation of additional interpreters (using <a class="reference internal" href="#c.Py_NewInterpreter" title="Py_NewInterpreter"><code>Py_NewInterpreter()</code></a>), but mixing multiple interpreters and the <code>PyGILState_*</code> API is unsupported.</p> </section> <section id="cautions-about-fork"> <span id="fork-and-threads"></span><h3>Cautions about fork()</h3> <p>Another important thing to note about threads is their behaviour in the face of the C <code>fork()</code> call. On most systems with <code>fork()</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#os.fork" title="os.fork"><code>os.fork()</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#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>pthread_atfork()</code> would need to be used to accomplish the same thing. Additionally, when extending or embedding Python, calling <code>fork()</code> directly rather than through <a class="reference internal" href="../library/os#os.fork" title="os.fork"><code>os.fork()</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#c.PyOS_AfterFork_Child" title="PyOS_AfterFork_Child"><code>PyOS_AfterFork_Child()</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#os.fork" title="os.fork"><code>os.fork()</code></a> does. This means finalizing all other <a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><code>PyThreadState</code></a> objects belonging to the current interpreter and all other <a class="reference internal" href="#c.PyInterpreterState" title="PyInterpreterState"><code>PyInterpreterState</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>fork()</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>exec()</code> will be called immediately after.</p> </section> <section id="high-level-api"> <h3>High-level API</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">
<code>type PyInterpreterState</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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> </dd>
</dl> <dl class="c type"> <dt class="sig sig-object c" id="c.PyThreadState">
<code>type PyThreadState</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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">
<code>PyInterpreterState *interp</code> </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">
<code>void PyEval_InitThreads()</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p id="index-37">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>Py_Initialize()</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>Py_Initialize()</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-38"></span>
</dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PyEval_ThreadsInitialized">
<code>int PyEval_ThreadsInitialized()</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Returns a non-zero value if <a class="reference internal" href="#c.PyEval_InitThreads" title="PyEval_InitThreads"><code>PyEval_InitThreads()</code></a> has been called. This function can be called without holding the GIL, and therefore can be used to avoid calls to the locking API when running single-threaded.</p> <div class="versionchanged"> <p><span class="versionmodified changed">Changed in version 3.7: </span>The <a class="reference internal" href="../glossary#term-GIL"><span class="xref std std-term">GIL</span></a> is now initialized by <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code>Py_Initialize()</code></a>.</p> </div> <div class="deprecated"> <p><span class="versionmodified deprecated">Deprecated since version 3.9.</span></p> </div> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PyEval_SaveThread">
<code>PyThreadState *PyEval_SaveThread()</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Release the global interpreter lock (if it has been created) and reset the thread state to <code>NULL</code>, returning the previous thread state (which is not <code>NULL</code>). If the lock has been created, the current thread must have acquired it.</p> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PyEval_RestoreThread">
<code>void PyEval_RestoreThread(PyThreadState *tstate)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Acquire the global interpreter lock (if it has been created) and set the thread state to <em>tstate</em>, which must not be <code>NULL</code>. If the lock has been created, the current thread must not have acquired it, otherwise deadlock ensues.</p> <div class="admonition note"> <p class="admonition-title">Note</p> <p>Calling this function from a thread when the runtime is finalizing will terminate the thread, even if the thread was not created by Python. You can use <code>_Py_IsFinalizing()</code> or <a class="reference internal" href="../library/sys#sys.is_finalizing" title="sys.is_finalizing"><code>sys.is_finalizing()</code></a> to check if the interpreter is in process of being finalized before calling this function to avoid unwanted termination.</p> </div> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PyThreadState_Get">
<code>PyThreadState *PyThreadState_Get()</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Return the current thread state. The global interpreter lock must be held. When the current thread state is <code>NULL</code>, this issues a fatal error (so that the caller needn’t check for <code>NULL</code>).</p> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PyThreadState_Swap">
<code>PyThreadState *PyThreadState_Swap(PyThreadState *tstate)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Swap the current thread state with the thread state given by the argument <em>tstate</em>, which may be <code>NULL</code>. The global interpreter lock must be held and is not released.</p> </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">
<code>PyGILState_STATE PyGILState_Ensure()</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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 global interpreter lock. 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>PyGILState_Release()</code></a>. In general, other thread-related APIs may be used between <a class="reference internal" href="#c.PyGILState_Ensure" title="PyGILState_Ensure"><code>PyGILState_Ensure()</code></a> and <a class="reference internal" href="#c.PyGILState_Release" title="PyGILState_Release"><code>PyGILState_Release()</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>Py_BEGIN_ALLOW_THREADS</code></a> and <a class="reference internal" href="#c.Py_END_ALLOW_THREADS" title="Py_END_ALLOW_THREADS"><code>Py_END_ALLOW_THREADS</code></a> macros is acceptable.</p> <p>The return value is an opaque “handle” to the thread state when <a class="reference internal" href="#c.PyGILState_Ensure" title="PyGILState_Ensure"><code>PyGILState_Ensure()</code></a> was called, and must be passed to <a class="reference internal" href="#c.PyGILState_Release" title="PyGILState_Release"><code>PyGILState_Release()</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>PyGILState_Ensure()</code></a> must save the handle for its call to <a class="reference internal" href="#c.PyGILState_Release" title="PyGILState_Release"><code>PyGILState_Release()</code></a>.</p> <p>When the function returns, the current thread will hold the GIL and be able to call arbitrary Python code. Failure is a fatal error.</p> <div class="admonition note"> <p class="admonition-title">Note</p> <p>Calling this function from a thread when the runtime is finalizing will terminate the thread, even if the thread was not created by Python. You can use <code>_Py_IsFinalizing()</code> or <a class="reference internal" href="../library/sys#sys.is_finalizing" title="sys.is_finalizing"><code>sys.is_finalizing()</code></a> to check if the interpreter is in process of being finalized before calling this function to avoid unwanted termination.</p> </div> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PyGILState_Release">
<code>void PyGILState_Release(PyGILState_STATE)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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>PyGILState_Ensure()</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>PyGILState_Ensure()</code></a> must be matched by a call to <a class="reference internal" href="#c.PyGILState_Release" title="PyGILState_Release"><code>PyGILState_Release()</code></a> on the same thread.</p> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PyGILState_GetThisThreadState">
<code>PyThreadState *PyGILState_GetThisThreadState()</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Get the current thread state for this thread. May return <code>NULL</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> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PyGILState_Check">
<code>int PyGILState_Check()</code> </dt> <dd>
<p>Return <code>1</code> if the current thread is holding the GIL and <code>0</code> otherwise. This function can be called from any thread at any time. Only if it has had its Python thread state initialized and currently is holding the GIL will it return <code>1</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 GIL is locked can allow the caller to perform sensitive actions or otherwise behave differently.</p> <div class="versionadded"> <p><span class="versionmodified added">New 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">
<code>Py_BEGIN_ALLOW_THREADS</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>This macro expands to <code>{ PyThreadState *_save; _save = PyEval_SaveThread();</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>Py_END_ALLOW_THREADS</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">
<code>Py_END_ALLOW_THREADS</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>This macro expands to <code>PyEval_RestoreThread(_save); }</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>Py_BEGIN_ALLOW_THREADS</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">
<code>Py_BLOCK_THREADS</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>This macro expands to <code>PyEval_RestoreThread(_save);</code>: it is equivalent to <a class="reference internal" href="#c.Py_END_ALLOW_THREADS" title="Py_END_ALLOW_THREADS"><code>Py_END_ALLOW_THREADS</code></a> without the closing brace.</p> </dd>
</dl> <dl class="c macro"> <dt class="sig sig-object c" id="c.Py_UNBLOCK_THREADS">
<code>Py_UNBLOCK_THREADS</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>This macro expands to <code>_save = PyEval_SaveThread();</code>: it is equivalent to <a class="reference internal" href="#c.Py_BEGIN_ALLOW_THREADS" title="Py_BEGIN_ALLOW_THREADS"><code>Py_BEGIN_ALLOW_THREADS</code></a> without the opening brace and variable declaration.</p> </dd>
</dl> </section> <section id="low-level-api"> <h3>Low-level API</h3> <p>All of the following functions must be called after <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code>Py_Initialize()</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>Py_Initialize()</code></a> now initializes the <a class="reference internal" href="../glossary#term-GIL"><span class="xref std std-term">GIL</span></a>.</p> </div> <dl class="c function"> <dt class="sig sig-object c" id="c.PyInterpreterState_New">
<code>PyInterpreterState *PyInterpreterState_New()</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Create a new interpreter state object. The global interpreter lock need not be held, but may be held if it is necessary to serialize calls to this function.</p> <p class="audit-hook">Raises an <a class="reference internal" href="../library/sys#auditing"><span class="std std-ref">auditing event</span></a> <code>cpython.PyInterpreterState_New</code> with no arguments.</p> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PyInterpreterState_Clear">
<code>void PyInterpreterState_Clear(PyInterpreterState *interp)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Reset all information in an interpreter state object. The global interpreter lock must be held.</p> <p class="audit-hook">Raises an <a class="reference internal" href="../library/sys#auditing"><span class="std std-ref">auditing event</span></a> <code>cpython.PyInterpreterState_Clear</code> with no arguments.</p> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PyInterpreterState_Delete">
<code>void PyInterpreterState_Delete(PyInterpreterState *interp)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Destroy an interpreter state object. The global interpreter lock need not be held. The interpreter state must have been reset with a previous call to <a class="reference internal" href="#c.PyInterpreterState_Clear" title="PyInterpreterState_Clear"><code>PyInterpreterState_Clear()</code></a>.</p> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PyThreadState_New">
<code>PyThreadState *PyThreadState_New(PyInterpreterState *interp)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Create a new thread state object belonging to the given interpreter object. The global interpreter lock need not be held, but may be held if it is necessary to serialize calls to this function.</p> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PyThreadState_Clear">
<code>void PyThreadState_Clear(PyThreadState *tstate)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Reset all information in a thread state object. The global interpreter lock must be held.</p> <div class="versionchanged"> <p><span class="versionmodified changed">Changed in version 3.9: </span>This function now calls the <code>PyThreadState.on_delete</code> callback. Previously, that happened in <a class="reference internal" href="#c.PyThreadState_Delete" title="PyThreadState_Delete"><code>PyThreadState_Delete()</code></a>.</p> </div> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PyThreadState_Delete">
<code>void PyThreadState_Delete(PyThreadState *tstate)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Destroy a thread state object. The global interpreter lock need not be held. The thread state must have been reset with a previous call to <a class="reference internal" href="#c.PyThreadState_Clear" title="PyThreadState_Clear"><code>PyThreadState_Clear()</code></a>.</p> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PyThreadState_DeleteCurrent">
<code>void PyThreadState_DeleteCurrent(void)</code> </dt> <dd>
<p>Destroy the current thread state and release the global interpreter lock. Like <a class="reference internal" href="#c.PyThreadState_Delete" title="PyThreadState_Delete"><code>PyThreadState_Delete()</code></a>, the global interpreter lock need not be held. The thread state must have been reset with a previous call to <a class="reference internal" href="#c.PyThreadState_Clear" title="PyThreadState_Clear"><code>PyThreadState_Clear()</code></a>.</p> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PyThreadState_GetFrame">
<code>PyFrameObject *PyThreadState_GetFrame(PyThreadState *tstate)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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#term-strong-reference"><span class="xref std std-term">strong reference</span></a>. Return <code>NULL</code> if no frame is currently executing.</p> <p>See also <a class="reference internal" href="reflection#c.PyEval_GetFrame" title="PyEval_GetFrame"><code>PyEval_GetFrame()</code></a>.</p> <p><em>tstate</em> must not be <code>NULL</code>.</p> <div class="versionadded"> <p><span class="versionmodified added">New in version 3.9.</span></p> </div> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PyThreadState_GetID">
<code>uint64_t PyThreadState_GetID(PyThreadState *tstate)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.10.</em><p>Get the unique thread state identifier of the Python thread state <em>tstate</em>.</p> <p><em>tstate</em> must not be <code>NULL</code>.</p> <div class="versionadded"> <p><span class="versionmodified added">New in version 3.9.</span></p> </div> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PyThreadState_GetInterpreter">
<code>PyInterpreterState *PyThreadState_GetInterpreter(PyThreadState *tstate)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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>NULL</code>.</p> <div class="versionadded"> <p><span class="versionmodified added">New in version 3.9.</span></p> </div> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PyThreadState_EnterTracing">
<code>void PyThreadState_EnterTracing(PyThreadState *tstate)</code> </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>PyThreadState_LeaveTracing()</code></a> function.</p> <div class="versionadded"> <p><span class="versionmodified added">New in version 3.11.</span></p> </div> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PyThreadState_LeaveTracing">
<code>void PyThreadState_LeaveTracing(PyThreadState *tstate)</code> </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>PyThreadState_EnterTracing()</code></a> function.</p> <p>See also <a class="reference internal" href="#c.PyEval_SetTrace" title="PyEval_SetTrace"><code>PyEval_SetTrace()</code></a> and <a class="reference internal" href="#c.PyEval_SetProfile" title="PyEval_SetProfile"><code>PyEval_SetProfile()</code></a> functions.</p> <div class="versionadded"> <p><span class="versionmodified added">New in version 3.11.</span></p> </div> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PyInterpreterState_Get">
<code>PyInterpreterState *PyInterpreterState_Get(void)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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 current Python thread state or no current interpreter. It cannot return NULL.</p> <p>The caller must hold the GIL.</p> <div class="versionadded"> <p><span class="versionmodified added">New in version 3.9.</span></p> </div> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PyInterpreterState_GetID">
<code>int64_t PyInterpreterState_GetID(PyInterpreterState *interp)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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>-1</code> is returned and an error is set.</p> <p>The caller must hold the GIL.</p> <div class="versionadded"> <p><span class="versionmodified added">New in version 3.7.</span></p> </div> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PyInterpreterState_GetDict">
<code>PyObject *PyInterpreterState_GetDict(PyInterpreterState *interp)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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>NULL</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#c.PyModule_GetState" title="PyModule_GetState"><code>PyModule_GetState()</code></a>, which extensions should use to store interpreter-specific state information.</p> <div class="versionadded"> <p><span class="versionmodified added">New in version 3.8.</span></p> </div> </dd>
</dl> <dl class="c type"> <dt class="sig sig-object c" id="c._PyFrameEvalFunction">
<code>typedef PyObject *(*_PyFrameEvalFunction)(PyThreadState *tstate, _PyInterpreterFrame *frame, int throwflag)</code> </dt> <dd>
<p>Type of a frame evaluation function.</p> <p>The <em>throwflag</em> parameter is used by the <code>throw()</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>PyFrameObject*</code> to <code>_PyInterpreterFrame*</code>.</p> </div> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c._PyInterpreterState_GetEvalFrameFunc">
<code>_PyFrameEvalFunction _PyInterpreterState_GetEvalFrameFunc(PyInterpreterState *interp)</code> </dt> <dd>
<p>Get the frame evaluation function.</p> <p>See the <span class="target" id="index-39"></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">New in version 3.9.</span></p> </div> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c._PyInterpreterState_SetEvalFrameFunc">
<code>void _PyInterpreterState_SetEvalFrameFunc(PyInterpreterState *interp, _PyFrameEvalFunction eval_frame)</code> </dt> <dd>
<p>Set the frame evaluation function.</p> <p>See the <span class="target" id="index-40"></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">New in version 3.9.</span></p> </div> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PyThreadState_GetDict">
<code>PyObject *PyThreadState_GetDict()</code> </dt> <dd>
<em class="refcount">Return value: Borrowed reference.</em><em class="stableabi"> Part of the <a class="reference internal" href="stable#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 current thread state is available. If this function returns <code>NULL</code>, no exception has been raised and the caller should assume no current thread state is available.</p> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PyThreadState_SetAsyncExc">
<code>int PyThreadState_SetAsyncExc(unsigned long id, PyObject *exc)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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 the GIL held. 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>NULL</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">
<code>void PyEval_AcquireThread(PyThreadState *tstate)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Acquire the global interpreter lock and set the current thread state to <em>tstate</em>, which must not be <code>NULL</code>. The lock must have been created earlier. If this thread already has the lock, deadlock ensues.</p> <div class="admonition note"> <p class="admonition-title">Note</p> <p>Calling this function from a thread when the runtime is finalizing will terminate the thread, even if the thread was not created by Python. You can use <code>_Py_IsFinalizing()</code> or <a class="reference internal" href="../library/sys#sys.is_finalizing" title="sys.is_finalizing"><code>sys.is_finalizing()</code></a> to check if the interpreter is in process of being finalized before calling this function to avoid unwanted termination.</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>PyEval_RestoreThread()</code></a>, <a class="reference internal" href="#c.Py_END_ALLOW_THREADS" title="Py_END_ALLOW_THREADS"><code>Py_END_ALLOW_THREADS()</code></a>, and <a class="reference internal" href="#c.PyGILState_Ensure" title="PyGILState_Ensure"><code>PyGILState_Ensure()</code></a>, and terminate the current thread if called while the interpreter is finalizing.</p> </div> <p><a class="reference internal" href="#c.PyEval_RestoreThread" title="PyEval_RestoreThread"><code>PyEval_RestoreThread()</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">
<code>void PyEval_ReleaseThread(PyThreadState *tstate)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Reset the current thread state to <code>NULL</code> and release the global interpreter lock. The lock must have been created earlier and must be held by the current thread. The <em>tstate</em> argument, which must not be <code>NULL</code>, is only used to check that it represents the current thread state — if it isn’t, a fatal error is reported.</p> <p><a class="reference internal" href="#c.PyEval_SaveThread" title="PyEval_SaveThread"><code>PyEval_SaveThread()</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_AcquireLock">
<code>void PyEval_AcquireLock()</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Acquire the global interpreter lock. The lock must have been created earlier. If this thread already has the lock, a deadlock ensues.</p> <div class="deprecated"> <p><span class="versionmodified deprecated">Deprecated since version 3.2: </span>This function does not update the current thread state. Please use <a class="reference internal" href="#c.PyEval_RestoreThread" title="PyEval_RestoreThread"><code>PyEval_RestoreThread()</code></a> or <a class="reference internal" href="#c.PyEval_AcquireThread" title="PyEval_AcquireThread"><code>PyEval_AcquireThread()</code></a> instead.</p> </div> <div class="admonition note"> <p class="admonition-title">Note</p> <p>Calling this function from a thread when the runtime is finalizing will terminate the thread, even if the thread was not created by Python. You can use <code>_Py_IsFinalizing()</code> or <a class="reference internal" href="../library/sys#sys.is_finalizing" title="sys.is_finalizing"><code>sys.is_finalizing()</code></a> to check if the interpreter is in process of being finalized before calling this function to avoid unwanted termination.</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>PyEval_RestoreThread()</code></a>, <a class="reference internal" href="#c.Py_END_ALLOW_THREADS" title="Py_END_ALLOW_THREADS"><code>Py_END_ALLOW_THREADS()</code></a>, and <a class="reference internal" href="#c.PyGILState_Ensure" title="PyGILState_Ensure"><code>PyGILState_Ensure()</code></a>, and terminate the current thread if called while the interpreter is finalizing.</p> </div> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PyEval_ReleaseLock">
<code>void PyEval_ReleaseLock()</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Release the global interpreter lock. The lock must have been created earlier.</p> <div class="deprecated"> <p><span class="versionmodified deprecated">Deprecated since version 3.2: </span>This function does not update the current thread state. Please use <a class="reference internal" href="#c.PyEval_SaveThread" title="PyEval_SaveThread"><code>PyEval_SaveThread()</code></a> or <a class="reference internal" href="#c.PyEval_ReleaseThread" title="PyEval_ReleaseThread"><code>PyEval_ReleaseThread()</code></a> instead.</p> </div> </dd>
</dl> </section> </section> <section id="sub-interpreter-support"> <span id="id1"></span><h2>Sub-interpreter support</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>PyInterpreterState_Main()</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>PyThreadState_Swap()</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">
<code>type PyInterpreterConfig</code> </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>Py_NewInterpreterFromConfig()</code></a> and never modified by the runtime.</p> <div class="versionadded"> <p><span class="versionmodified added">New 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">
<code>int use_main_obmalloc</code> </dt> <dd>
<p>If this is <code>0</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>0</code> then <a class="reference internal" href="#c.PyInterpreterConfig.check_multi_interp_extensions" title="PyInterpreterConfig.check_multi_interp_extensions"><code>check_multi_interp_extensions</code></a> must be <code>1</code> (non-zero). If this is <code>1</code> then <a class="reference internal" href="#c.PyInterpreterConfig.gil" title="PyInterpreterConfig.gil"><code>gil</code></a> must not be <a class="reference internal" href="#c.PyInterpreterConfig_OWN_GIL" title="PyInterpreterConfig_OWN_GIL"><code>PyInterpreterConfig_OWN_GIL</code></a>.</p> </dd>
</dl> <dl class="c member"> <dt class="sig sig-object c" id="c.PyInterpreterConfig.allow_fork">
<code>int allow_fork</code> </dt> <dd>
<p>If this is <code>0</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#module-subprocess" title="subprocess: Subprocess management."><code>subprocess</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">
<code>int allow_exec</code> </dt> <dd>
<p>If this is <code>0</code> then the runtime will not support replacing the current process via exec (e.g. <a class="reference internal" href="../library/os#os.execv" title="os.execv"><code>os.execv()</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#module-subprocess" title="subprocess: Subprocess management."><code>subprocess</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">
<code>int allow_threads</code> </dt> <dd>
<p>If this is <code>0</code> then the sub-interpreter’s <a class="reference internal" href="../library/threading#module-threading" title="threading: Thread-based parallelism."><code>threading</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">
<code>int allow_daemon_threads</code> </dt> <dd>
<p>If this is <code>0</code> then the sub-interpreter’s <a class="reference internal" href="../library/threading#module-threading" title="threading: Thread-based parallelism."><code>threading</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>allow_threads</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">
<code>int check_multi_interp_extensions</code> </dt> <dd>
<p>If this is <code>0</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-41"></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#c.Py_mod_multiple_interpreters" title="Py_mod_multiple_interpreters"><code>Py_mod_multiple_interpreters</code></a>.)</p> <p>This must be <code>1</code> (non-zero) if <a class="reference internal" href="#c.PyInterpreterConfig.use_main_obmalloc" title="PyInterpreterConfig.use_main_obmalloc"><code>use_main_obmalloc</code></a> is <code>0</code>.</p> </dd>
</dl> <dl class="c member"> <dt class="sig sig-object c" id="c.PyInterpreterConfig.gil">
<code>int gil</code> </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">
<code>PyInterpreterConfig_DEFAULT_GIL</code> </dt> <dd>
<p>Use the default selection (<a class="reference internal" href="#c.PyInterpreterConfig_SHARED_GIL" title="PyInterpreterConfig_SHARED_GIL"><code>PyInterpreterConfig_SHARED_GIL</code></a>).</p> </dd>
</dl> <dl class="c macro"> <dt class="sig sig-object c" id="c.PyInterpreterConfig_SHARED_GIL">
<code>PyInterpreterConfig_SHARED_GIL</code> </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">
<code>PyInterpreterConfig_OWN_GIL</code> </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>PyInterpreterConfig_OWN_GIL</code></a> then <a class="reference internal" href="#c.PyInterpreterConfig.use_main_obmalloc" title="PyInterpreterConfig.use_main_obmalloc"><code>PyInterpreterConfig.use_main_obmalloc</code></a> must be <code>0</code>.</p> </dd>
</dl> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.Py_NewInterpreterFromConfig">
<code>PyStatus Py_NewInterpreterFromConfig(PyThreadState **tstate_p, const PyInterpreterConfig *config)</code> </dt> <dd>
<p id="index-42">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#module-builtins" title="builtins: The module that provides the built-in namespace."><code>builtins</code></a>, <a class="reference internal" href="../library/__main__#module-__main__" title="__main__: The environment where top-level code is run. Covers command-line interfaces, import-time behavior, and ``__name__ == '__main__'``."><code>__main__</code></a> and <a class="reference internal" href="../library/sys#module-sys" title="sys: Access system-specific parameters and functions."><code>sys</code></a>. The table of loaded modules (<code>sys.modules</code>) and the module search path (<code>sys.path</code>) are also separate. The new environment has no <code>sys.argv</code> variable. It has new standard I/O stream file objects <code>sys.stdin</code>, <code>sys.stdout</code> and <code>sys.stderr</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 thread state created in the new sub-interpreter. This thread state is made in the current thread state. 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>NULL</code>; no exception is set since the exception state is stored in the current thread state and there may not be a current thread state.</p> <p>Like all other Python/C API functions, the global interpreter lock must be held before calling this function and is still held when it returns. Likewise a current thread state must be set on entry. On success, the returned thread state will be set as current. If the sub-interpreter is created with its own GIL then the GIL of the calling interpreter will be released. When the function returns, the new interpreter’s GIL will be held by the current thread and the previously interpreter’s GIL will remain released here.</p> <div class="versionadded"> <p><span class="versionmodified added">New in version 3.12.</span></p> </div> <p>Sub-interpreters are most effective when isolated from each other, with certain functionality restricted:</p> <pre data-language="c">PyInterpreterConfig config = {
    .use_main_obmalloc = 0,
    .allow_fork = 0,
    .allow_exec = 0,
    .allow_threads = 1,
    .allow_daemon_threads = 0,
    .check_multi_interp_extensions = 1,
    .gil = PyInterpreterConfig_OWN_GIL,
};
PyThreadState *tstate = Py_NewInterpreterFromConfig(&amp;config);
</pre> <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>PyInterpreterState</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>PyInterpreterState</code></a>.</p> <p id="index-43">Extension modules are shared between (sub-)interpreters as follows:</p> <ul> <li>For modules using multi-phase initialization, e.g. <a class="reference internal" href="module#c.PyModule_FromDefAndSpec" title="PyModule_FromDefAndSpec"><code>PyModule_FromDefAndSpec()</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.</li> <li>
<p>For modules using single-phase initialization, e.g. <a class="reference internal" href="module#c.PyModule_Create" title="PyModule_Create"><code>PyModule_Create()</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>init</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>Py_FinalizeEx()</code></a> and <a class="reference internal" href="#c.Py_Initialize" title="Py_Initialize"><code>Py_Initialize()</code></a>; in that case, the extension’s <code>initmodule</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-44"></span>
</dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.Py_NewInterpreter">
<code>PyThreadState *Py_NewInterpreter(void)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p id="index-45">Create a new sub-interpreter. This is essentially just a wrapper around <a class="reference internal" href="#c.Py_NewInterpreterFromConfig" title="Py_NewInterpreterFromConfig"><code>Py_NewInterpreterFromConfig()</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">
<code>void Py_EndInterpreter(PyThreadState *tstate)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p id="index-46">Destroy the (sub-)interpreter represented by the given thread state. The given thread state must be the current thread state. See the discussion of thread states below. When the call returns, the current thread state is <code>NULL</code>. All thread states associated with this interpreter are destroyed. The global interpreter lock used by the target interpreter must be held before calling this function. No GIL is held when it returns.</p> <p><a class="reference internal" href="#c.Py_FinalizeEx" title="Py_FinalizeEx"><code>Py_FinalizeEx()</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"> <h3>A Per-Interpreter GIL</h3> <p>Using <a class="reference internal" href="#c.Py_NewInterpreterFromConfig" title="Py_NewInterpreterFromConfig"><code>Py_NewInterpreterFromConfig()</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-47"></span><a class="pep reference external" href="https://peps.python.org/pep-0554/"><strong>PEP 554</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>None</code>, <code>(1, 5)</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 “immortal”. 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">New in version 3.12.</span></p> </div> </section> <section id="bugs-and-caveats"> <h3>Bugs and caveats</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#os.close" title="os.close"><code>os.close()</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>PyGILState_*</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>PyGILState_Ensure()</code></a> and <a class="reference internal" href="#c.PyGILState_Release" title="PyGILState_Release"><code>PyGILState_Release()</code></a> calls. Furthermore, extensions (such as <a class="reference internal" href="../library/ctypes#module-ctypes" title="ctypes: A foreign function library for Python."><code>ctypes</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</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">
<code>int Py_AddPendingCall(int (*func)(void*), void *arg)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p id="index-48">Schedule a function to be called from the main interpreter thread. On success, <code>0</code> is returned and <em>func</em> is queued for being called in the main thread. On failure, <code>-1</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>on a <a class="reference internal" href="../glossary#term-bytecode"><span class="xref std std-term">bytecode</span></a> boundary;</li> <li>with the main thread holding the <a class="reference internal" href="../glossary#term-global-interpreter-lock"><span class="xref std std-term">global interpreter lock</span></a> (<em>func</em> can therefore use the full C API).</li> </ul> <p><em>func</em> must return <code>0</code> on success, or <code>-1</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 global interpreter lock is released.</p> <p>This function doesn’t need a current thread state to run, and it doesn’t need the global interpreter lock.</p> <p>To call this function in a subinterpreter, the caller must hold the GIL. 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="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="versionadded"> <p><span class="versionmodified added">New in version 3.1.</span></p> </div> </dd>
</dl> </section> <section id="profiling-and-tracing"> <span id="profiling"></span><h2>Profiling and Tracing</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">
<code>typedef int (*Py_tracefunc)(PyObject *obj, PyFrameObject *frame, int what, PyObject *arg)</code> </dt> <dd>
<p>The type of the trace function registered using <a class="reference internal" href="#c.PyEval_SetProfile" title="PyEval_SetProfile"><code>PyEval_SetProfile()</code></a> and <a class="reference internal" href="#c.PyEval_SetTrace" title="PyEval_SetTrace"><code>PyEval_SetTrace()</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>PyTrace_CALL</code></a>, <a class="reference internal" href="#c.PyTrace_EXCEPTION" title="PyTrace_EXCEPTION"><code>PyTrace_EXCEPTION</code></a>, <a class="reference internal" href="#c.PyTrace_LINE" title="PyTrace_LINE"><code>PyTrace_LINE</code></a>, <a class="reference internal" href="#c.PyTrace_RETURN" title="PyTrace_RETURN"><code>PyTrace_RETURN</code></a>, <a class="reference internal" href="#c.PyTrace_C_CALL" title="PyTrace_C_CALL"><code>PyTrace_C_CALL</code></a>, <a class="reference internal" href="#c.PyTrace_C_EXCEPTION" title="PyTrace_C_EXCEPTION"><code>PyTrace_C_EXCEPTION</code></a>, <a class="reference internal" href="#c.PyTrace_C_RETURN" title="PyTrace_C_RETURN"><code>PyTrace_C_RETURN</code></a>, or <a class="reference internal" href="#c.PyTrace_OPCODE" title="PyTrace_OPCODE"><code>PyTrace_OPCODE</code></a>, and <em>arg</em> depends on the value of <em>what</em>:</p> <table class="docutils align-default">  <thead> <tr>
<th class="head"><p>Value of <em>what</em></p></th> <th class="head"><p>Meaning of <em>arg</em></p></th> </tr> </thead>  <tr>
<td><p><a class="reference internal" href="#c.PyTrace_CALL" title="PyTrace_CALL"><code>PyTrace_CALL</code></a></p></td> <td><p>Always <a class="reference internal" href="none#c.Py_None" title="Py_None"><code>Py_None</code></a>.</p></td> </tr> <tr>
<td><p><a class="reference internal" href="#c.PyTrace_EXCEPTION" title="PyTrace_EXCEPTION"><code>PyTrace_EXCEPTION</code></a></p></td> <td><p>Exception information as returned by <a class="reference internal" href="../library/sys#sys.exc_info" title="sys.exc_info"><code>sys.exc_info()</code></a>.</p></td> </tr> <tr>
<td><p><a class="reference internal" href="#c.PyTrace_LINE" title="PyTrace_LINE"><code>PyTrace_LINE</code></a></p></td> <td><p>Always <a class="reference internal" href="none#c.Py_None" title="Py_None"><code>Py_None</code></a>.</p></td> </tr> <tr>
<td><p><a class="reference internal" href="#c.PyTrace_RETURN" title="PyTrace_RETURN"><code>PyTrace_RETURN</code></a></p></td> <td><p>Value being returned to the caller, or <code>NULL</code> if caused by an exception.</p></td> </tr> <tr>
<td><p><a class="reference internal" href="#c.PyTrace_C_CALL" title="PyTrace_C_CALL"><code>PyTrace_C_CALL</code></a></p></td> <td><p>Function object being called.</p></td> </tr> <tr>
<td><p><a class="reference internal" href="#c.PyTrace_C_EXCEPTION" title="PyTrace_C_EXCEPTION"><code>PyTrace_C_EXCEPTION</code></a></p></td> <td><p>Function object being called.</p></td> </tr> <tr>
<td><p><a class="reference internal" href="#c.PyTrace_C_RETURN" title="PyTrace_C_RETURN"><code>PyTrace_C_RETURN</code></a></p></td> <td><p>Function object being called.</p></td> </tr> <tr>
<td><p><a class="reference internal" href="#c.PyTrace_OPCODE" title="PyTrace_OPCODE"><code>PyTrace_OPCODE</code></a></p></td> <td><p>Always <a class="reference internal" href="none#c.Py_None" title="Py_None"><code>Py_None</code></a>.</p></td> </tr>  </table> </dd>
</dl> <dl class="c var"> <dt class="sig sig-object c" id="c.PyTrace_CALL">
<code>int PyTrace_CALL</code> </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>Py_tracefunc</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">
<code>int PyTrace_EXCEPTION</code> </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>Py_tracefunc</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">
<code>int PyTrace_LINE</code> </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>Py_tracefunc</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#frame.f_trace_lines" title="frame.f_trace_lines"><code>f_trace_lines</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">
<code>int PyTrace_RETURN</code> </dt> <dd>
<p>The value for the <em>what</em> parameter to <a class="reference internal" href="#c.Py_tracefunc" title="Py_tracefunc"><code>Py_tracefunc</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">
<code>int PyTrace_C_CALL</code> </dt> <dd>
<p>The value for the <em>what</em> parameter to <a class="reference internal" href="#c.Py_tracefunc" title="Py_tracefunc"><code>Py_tracefunc</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">
<code>int PyTrace_C_EXCEPTION</code> </dt> <dd>
<p>The value for the <em>what</em> parameter to <a class="reference internal" href="#c.Py_tracefunc" title="Py_tracefunc"><code>Py_tracefunc</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">
<code>int PyTrace_C_RETURN</code> </dt> <dd>
<p>The value for the <em>what</em> parameter to <a class="reference internal" href="#c.Py_tracefunc" title="Py_tracefunc"><code>Py_tracefunc</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">
<code>int PyTrace_OPCODE</code> </dt> <dd>
<p>The value for the <em>what</em> parameter to <a class="reference internal" href="#c.Py_tracefunc" title="Py_tracefunc"><code>Py_tracefunc</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#frame.f_trace_opcodes" title="frame.f_trace_opcodes"><code>f_trace_opcodes</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">
<code>void PyEval_SetProfile(Py_tracefunc func, PyObject *obj)</code> </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>NULL</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>PyTrace_LINE</code></a> <a class="reference internal" href="#c.PyTrace_OPCODE" title="PyTrace_OPCODE"><code>PyTrace_OPCODE</code></a> and <a class="reference internal" href="#c.PyTrace_EXCEPTION" title="PyTrace_EXCEPTION"><code>PyTrace_EXCEPTION</code></a>.</p> <p>See also the <a class="reference internal" href="../library/sys#sys.setprofile" title="sys.setprofile"><code>sys.setprofile()</code></a> function.</p> <p>The caller must hold the <a class="reference internal" href="../glossary#term-GIL"><span class="xref std std-term">GIL</span></a>.</p> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PyEval_SetProfileAllThreads">
<code>void PyEval_SetProfileAllThreads(Py_tracefunc func, PyObject *obj)</code> </dt> <dd>
<p>Like <a class="reference internal" href="#c.PyEval_SetProfile" title="PyEval_SetProfile"><code>PyEval_SetProfile()</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 hold the <a class="reference internal" href="../glossary#term-GIL"><span class="xref std std-term">GIL</span></a>.</p> <p>As <a class="reference internal" href="#c.PyEval_SetProfile" title="PyEval_SetProfile"><code>PyEval_SetProfile()</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">New in version 3.12.</span></p> </div> <dl class="c function"> <dt class="sig sig-object c" id="c.PyEval_SetTrace">
<code>void PyEval_SetTrace(Py_tracefunc func, PyObject *obj)</code> </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>PyEval_SetProfile()</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>PyEval_SetTrace()</code></a> will not receive <a class="reference internal" href="#c.PyTrace_C_CALL" title="PyTrace_C_CALL"><code>PyTrace_C_CALL</code></a>, <a class="reference internal" href="#c.PyTrace_C_EXCEPTION" title="PyTrace_C_EXCEPTION"><code>PyTrace_C_EXCEPTION</code></a> or <a class="reference internal" href="#c.PyTrace_C_RETURN" title="PyTrace_C_RETURN"><code>PyTrace_C_RETURN</code></a> as a value for the <em>what</em> parameter.</p> <p>See also the <a class="reference internal" href="../library/sys#sys.settrace" title="sys.settrace"><code>sys.settrace()</code></a> function.</p> <p>The caller must hold the <a class="reference internal" href="../glossary#term-GIL"><span class="xref std std-term">GIL</span></a>.</p> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PyEval_SetTraceAllThreads">
<code>void PyEval_SetTraceAllThreads(Py_tracefunc func, PyObject *obj)</code> </dt> <dd>
<p>Like <a class="reference internal" href="#c.PyEval_SetTrace" title="PyEval_SetTrace"><code>PyEval_SetTrace()</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 hold the <a class="reference internal" href="../glossary#term-GIL"><span class="xref std std-term">GIL</span></a>.</p> <p>As <a class="reference internal" href="#c.PyEval_SetTrace" title="PyEval_SetTrace"><code>PyEval_SetTrace()</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">New in version 3.12.</span></p> </div> </section> <section id="advanced-debugger-support"> <span id="advanced-debugging"></span><h2>Advanced Debugger Support</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">
<code>PyInterpreterState *PyInterpreterState_Head()</code> </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">
<code>PyInterpreterState *PyInterpreterState_Main()</code> </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">
<code>PyInterpreterState *PyInterpreterState_Next(PyInterpreterState *interp)</code> </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">
<code>PyThreadState *PyInterpreterState_ThreadHead(PyInterpreterState *interp)</code> </dt> <dd>
<p>Return the pointer to the first <a class="reference internal" href="#c.PyThreadState" title="PyThreadState"><code>PyThreadState</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">
<code>PyThreadState *PyThreadState_Next(PyThreadState *tstate)</code> </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>PyInterpreterState</code></a> object.</p> </dd>
</dl> </section> <section id="thread-local-storage-support"> <span id="thread-local-storage"></span><h2>Thread Local Storage Support</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#threading.local" title="threading.local"><code>threading.local</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>The GIL does <em>not</em> need to be held when calling these functions; they supply their own locking.</p> <p>Note that <code>Python.h</code> does not include the declaration of the TLS APIs, you need to include <code>pythread.h</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#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</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>Py_tss_t</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">New 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-49"></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">
<code>type Py_tss_t</code> </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#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>Py_tss_NEEDS_INIT</code></a> is allowed.</p> </dd>
</dl> <dl class="c macro"> <dt class="sig sig-object c" id="c.Py_tss_NEEDS_INIT">
<code>Py_tss_NEEDS_INIT</code> </dt> <dd>
<p>This macro expands to the initializer for <a class="reference internal" href="#c.Py_tss_t" title="Py_tss_t"><code>Py_tss_t</code></a> variables. Note that this macro won’t be defined with <a class="reference internal" href="stable#stable"><span class="std std-ref">Py_LIMITED_API</span></a>.</p> </dd>
</dl> <section id="dynamic-allocation"> <h4>Dynamic Allocation</h4> <p>Dynamic allocation of the <a class="reference internal" href="#c.Py_tss_t" title="Py_tss_t"><code>Py_tss_t</code></a>, required in extension modules built with <a class="reference internal" href="stable#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">
<code>Py_tss_t *PyThread_tss_alloc()</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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>Py_tss_NEEDS_INIT</code></a>, or <code>NULL</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">
<code>void PyThread_tss_free(Py_tss_t *key)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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>PyThread_tss_alloc()</code></a>, after first calling <a class="reference internal" href="#c.PyThread_tss_delete" title="PyThread_tss_delete"><code>PyThread_tss_delete()</code></a> to ensure any associated thread locals have been unassigned. This is a no-op if the <em>key</em> argument is <code>NULL</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>NULL</code>.</p> </div> </dd>
</dl> </section> <section id="methods"> <h4>Methods</h4> <p>The parameter <em>key</em> of these functions must not be <code>NULL</code>. Moreover, the behaviors of <a class="reference internal" href="#c.PyThread_tss_set" title="PyThread_tss_set"><code>PyThread_tss_set()</code></a> and <a class="reference internal" href="#c.PyThread_tss_get" title="PyThread_tss_get"><code>PyThread_tss_get()</code></a> are undefined if the given <a class="reference internal" href="#c.Py_tss_t" title="Py_tss_t"><code>Py_tss_t</code></a> has not been initialized by <a class="reference internal" href="#c.PyThread_tss_create" title="PyThread_tss_create"><code>PyThread_tss_create()</code></a>.</p> <dl class="c function"> <dt class="sig sig-object c" id="c.PyThread_tss_is_created">
<code>int PyThread_tss_is_created(Py_tss_t *key)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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>Py_tss_t</code></a> has been initialized by <a class="reference internal" href="#c.PyThread_tss_create" title="PyThread_tss_create"><code>PyThread_tss_create()</code></a>.</p> </dd>
</dl> <dl class="c function"> <dt class="sig sig-object c" id="c.PyThread_tss_create">
<code>int PyThread_tss_create(Py_tss_t *key)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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>Py_tss_NEEDS_INIT</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">
<code>void PyThread_tss_delete(Py_tss_t *key)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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>PyThread_tss_create()</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">
<code>int PyThread_tss_set(Py_tss_t *key, void *value)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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">
<code>void *PyThread_tss_get(Py_tss_t *key)</code> </dt> <dd>
<em class="stableabi"> Part of the <a class="reference internal" href="stable#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>NULL</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</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>int</code>. On such platforms, <a class="reference internal" href="#c.PyThread_create_key" title="PyThread_create_key"><code>PyThread_create_key()</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">
<code>int PyThread_create_key()</code> </dt> <dd><em class="stableabi"> Part of the <a class="reference internal" href="stable#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">
<code>void PyThread_delete_key(int key)</code> </dt> <dd><em class="stableabi"> Part of the <a class="reference internal" href="stable#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">
<code>int PyThread_set_key_value(int key, void *value)</code> </dt> <dd><em class="stableabi"> Part of the <a class="reference internal" href="stable#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">
<code>void *PyThread_get_key_value(int key)</code> </dt> <dd><em class="stableabi"> Part of the <a class="reference internal" href="stable#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">
<code>void PyThread_delete_key_value(int key)</code> </dt> <dd><em class="stableabi"> Part of the <a class="reference internal" href="stable#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">
<code>void PyThread_ReInitTLS()</code> </dt> <dd><em class="stableabi"> Part of the <a class="reference internal" href="stable#stable"><span class="std std-ref">Stable ABI</span></a>.</em></dd>
</dl> </section> </section> <div class="_attribution">
  <p class="_attribution-p">
    &copy; 2001&ndash;2023 Python Software Foundation<br>Licensed under the PSF License.<br>
    <a href="https://docs.python.org/3.12/c-api/init.html" class="_attribution-link">https://docs.python.org/3.12/c-api/init.html</a>
  </p>
</div>