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Currently, two types exist – <a class="reference internal" href="../library/stdtypes.html#types-genericalias"><span class="std std-ref">GenericAlias</span></a> and <a class="reference internal" href="../library/stdtypes.html#types-union"><span class="std std-ref">Union</span></a>. Only <code class="docutils literal notranslate"><span class="pre">GenericAlias</span></code> is exposed to C.</p> <dl class="c function"> <dt class="sig sig-object c" id="c.Py_GenericAlias"> <a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">Py_GenericAlias</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">origin</span></span>, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">args</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_GenericAlias" title="Permalink to this definition">¶</a><br /></dt> <dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.9.</em><p>Create a <a class="reference internal" href="../library/stdtypes.html#types-genericalias"><span class="std std-ref">GenericAlias</span></a> object. Equivalent to calling the Python class <a class="reference internal" href="../library/types.html#types.GenericAlias" title="types.GenericAlias"><code class="xref py py-class docutils literal notranslate"><span class="pre">types.GenericAlias</span></code></a>. The <em>origin</em> and <em>args</em> arguments set the <code class="docutils literal notranslate"><span class="pre">GenericAlias</span></code>‘s <code class="docutils literal notranslate"><span class="pre">__origin__</span></code> and <code class="docutils literal notranslate"><span class="pre">__args__</span></code> attributes respectively. <em>origin</em> should be a <span class="c-expr sig sig-inline c"><a class="reference internal" href="type.html#c.PyTypeObject" title="PyTypeObject"><span class="n">PyTypeObject</span></a><span class="p">*</span></span>, and <em>args</em> can be a <span class="c-expr sig sig-inline c"><a class="reference internal" href="tuple.html#c.PyTupleObject" title="PyTupleObject"><span class="n">PyTupleObject</span></a><span class="p">*</span></span> or any <code class="docutils literal notranslate"><span class="pre">PyObject*</span></code>. If <em>args</em> passed is not a tuple, a 1-tuple is automatically constructed and <code class="docutils literal notranslate"><span class="pre">__args__</span></code> is set to <code class="docutils literal notranslate"><span class="pre">(args,)</span></code>. Minimal checking is done for the arguments, so the function will succeed even if <em>origin</em> is not a type. The <code class="docutils literal notranslate"><span class="pre">GenericAlias</span></code>‘s <code class="docutils literal notranslate"><span class="pre">__parameters__</span></code> attribute is constructed lazily from <code class="docutils literal notranslate"><span class="pre">__args__</span></code>. On failure, an exception is raised and <code class="docutils literal notranslate"><span class="pre">NULL</span></code> is returned.</p> <p>Here’s an example of how to make an extension type generic:</p> <div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="p">...</span><span class="w"></span> <span class="k">static</span><span class="w"> </span><span class="n">PyMethodDef</span><span class="w"> </span><span class="n">my_obj_methods</span><span class="p">[]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="w"></span> <span class="w"> </span><span class="c1">// Other methods.</span> <span class="w"> </span><span class="p">...</span><span class="w"></span> <span class="w"> </span><span class="p">{</span><span class="s">"__class_getitem__"</span><span class="p">,</span><span class="w"> </span><span class="p">(</span><span class="n">PyCFunction</span><span class="p">)</span><span class="n">Py_GenericAlias</span><span class="p">,</span><span class="w"> </span><span class="n">METH_O</span><span class="o">|</span><span class="n">METH_CLASS</span><span class="p">,</span><span class="w"> </span><span class="s">"See PEP 585"</span><span class="p">}</span><span class="w"></span> <span class="w"> </span><span class="p">...</span><span class="w"></span> <span class="p">}</span><span class="w"></span> </pre></div> </div> <div class="admonition seealso"> <p class="admonition-title">See also</p> <p>The data model method <code class="xref py py-meth docutils literal notranslate"><span class="pre">__class_getitem__()</span></code>.</p> </div> <div class="versionadded"> <p><span class="versionmodified added">New in version 3.9.</span></p> </div> </dd></dl> <dl class="c var"> <dt class="sig sig-object c" id="c.Py_GenericAliasType"> <a class="reference internal" href="type.html#c.PyTypeObject" title="PyTypeObject"><span class="n"><span class="pre">PyTypeObject</span></span></a><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_GenericAliasType</span></span></span><a class="headerlink" href="#c.Py_GenericAliasType" title="Permalink to this definition">¶</a><br /></dt> <dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.9.</em><p>The C type of the object returned by <a class="reference internal" href="#c.Py_GenericAlias" title="Py_GenericAlias"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_GenericAlias()</span></code></a>. Equivalent to <a class="reference internal" href="../library/types.html#types.GenericAlias" title="types.GenericAlias"><code class="xref py py-class docutils literal notranslate"><span class="pre">types.GenericAlias</span></code></a> in Python.</p> <div class="versionadded"> <p><span class="versionmodified added">New in version 3.9.</span></p> </div> </dd></dl> </section> <div class="clearer"></div> </div> </div> </div> <div class="sphinxsidebar" role="navigation" aria-label="main navigation"> <div class="sphinxsidebarwrapper"> <h4>Previous topic</h4> <p class="topless"><a href="datetime.html" title="previous chapter">DateTime Objects</a></p> <h4>Next topic</h4> <p class="topless"><a href="init.html" title="next chapter">Initialization, Finalization, and Threads</a></p> <div role="note" aria-label="source link"> <h3>This Page</h3> <ul class="this-page-menu"> <li><a href="../bugs.html">Report a Bug</a></li> <li> <a href="https://github.com/python/cpython/blob/3.10/Doc/c-api/typehints.rst" rel="nofollow">Show Source </a> </li> </ul> </div> </div> </div> <div class="clearer"></div> </div> <div class="related" role="navigation" aria-label="related navigation"> <h3>Navigation</h3> <ul> <li class="right" style="margin-right: 10px"> <a href="../genindex.html" title="General Index" >index</a></li> <li class="right" > <a href="../py-modindex.html" title="Python Module Index" >modules</a> |</li> <li class="right" > <a href="init.html" title="Initialization, Finalization, and Threads" >next</a> |</li> <li class="right" > <a href="datetime.html" title="DateTime Objects" >previous</a> |</li> <li><img src="../_static/py.svg" alt="python logo" style="vertical-align: middle; margin-top: -1px"/></li> <li><a href="https://www.python.org/">Python</a> »</li> <li class="switchers"> <div class="language_switcher_placeholder"></div> <div class="version_switcher_placeholder"></div> </li> <li> </li> <li id="cpython-language-and-version"> <a href="../index.html">3.10.12 Documentation</a> » </li> <li class="nav-item nav-item-1"><a href="index.html" >Python/C API Reference Manual</a> »</li> <li class="nav-item nav-item-2"><a href="concrete.html" >Concrete Objects Layer</a> »</li> <li class="nav-item nav-item-this"><a href="">Objects for Type Hinting</a></li> <li class="right"> <div class="inline-search" role="search"> <form class="inline-search" action="../search.html" method="get"> <input placeholder="Quick search" aria-label="Quick search" type="text" name="q" /> <input type="submit" value="Go" /> <input type="hidden" name="check_keywords" value="yes" /> <input type="hidden" name="area" value="default" /> </form> </div> | </li> </ul> </div> <div class="footer"> © <a href="../copyright.html">Copyright</a> 2001-2025, Python Software Foundation. <br /> This page is licensed under the Python Software Foundation License Version 2. <br /> Examples, recipes, and other code in the documentation are additionally licensed under the Zero Clause BSD License. <br /> See <a href="/license.html">History and License</a> for more information.<br /> <br /> The Python Software Foundation is a non-profit corporation. <a href="https://www.python.org/psf/donations/">Please donate.</a> <br /> <br /> Last updated on February 04, 2025. <a href="/bugs.html">Found a bug</a>? <br /> Created using <a href="https://www.sphinx-doc.org/">Sphinx</a> 4.3.2. </div> </body> </html>