Edit File: capsule.html
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>Capsules — Python 2.7.5 documentation</title> <link rel="stylesheet" href="../_static/default.css" type="text/css" /> <link rel="stylesheet" href="../_static/pygments.css" type="text/css" /> <script type="text/javascript"> var DOCUMENTATION_OPTIONS = { URL_ROOT: '../', VERSION: '2.7.5', COLLAPSE_INDEX: false, FILE_SUFFIX: '.html', HAS_SOURCE: true }; </script> <script type="text/javascript" src="../_static/jquery.js"></script> <script type="text/javascript" src="../_static/underscore.js"></script> <script type="text/javascript" src="../_static/doctools.js"></script> <script type="text/javascript" src="../_static/sidebar.js"></script> <link rel="search" type="application/opensearchdescription+xml" title="Search within Python 2.7.5 documentation" href="../_static/opensearch.xml"/> <link rel="author" title="About these documents" href="../about.html" /> <link rel="copyright" title="Copyright" href="../copyright.html" /> <link rel="top" title="Python 2.7.5 documentation" href="../index.html" /> <link rel="up" title="Concrete Objects Layer" href="concrete.html" /> <link rel="next" title="CObjects" href="cobject.html" /> <link rel="prev" title="Weak Reference Objects" href="weakref.html" /> <link rel="shortcut icon" type="image/png" href="../_static/py.png" /> <script type="text/javascript" src="../_static/copybutton.js"></script> </head> <body> <div class="related"> <h3>Navigation</h3> <ul> <li class="right" style="margin-right: 10px"> <a href="../genindex.html" title="General Index" accesskey="I">index</a></li> <li class="right" > <a href="../py-modindex.html" title="Python Module Index" >modules</a> |</li> <li class="right" > <a href="cobject.html" title="CObjects" accesskey="N">next</a> |</li> <li class="right" > <a href="weakref.html" title="Weak Reference Objects" accesskey="P">previous</a> |</li> <li><img src="../_static/py.png" alt="" style="vertical-align: middle; margin-top: -1px"/></li> <li><a href="http://www.python.org/">Python</a> »</li> <li> <a href="../index.html">Python 2.7.5 documentation</a> » </li> <li><a href="index.html" >Python/C API Reference Manual</a> »</li> <li><a href="concrete.html" accesskey="U">Concrete Objects Layer</a> »</li> </ul> </div> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body"> <div class="section" id="capsules"> <span id="id1"></span><h1>Capsules<a class="headerlink" href="#capsules" title="Permalink to this headline">¶</a></h1> <p id="index-0">Refer to <a class="reference internal" href="../extending/extending.html#using-capsules"><em>Providing a C API for an Extension Module</em></a> for more information on using these objects.</p> <dl class="type"> <dt id="PyCapsule"> <tt class="descname">PyCapsule</tt><a class="headerlink" href="#PyCapsule" title="Permalink to this definition">¶</a></dt> <dd><p>This subtype of <a class="reference internal" href="structures.html#PyObject" title="PyObject"><tt class="xref c c-type docutils literal"><span class="pre">PyObject</span></tt></a> represents an opaque value, useful for C extension modules who need to pass an opaque value (as a <tt class="xref c c-type docutils literal"><span class="pre">void*</span></tt> pointer) through Python code to other C code. It is often used to make a C function pointer defined in one module available to other modules, so the regular import mechanism can be used to access C APIs defined in dynamically loaded modules.</p> </dd></dl> <dl class="type"> <dt id="PyCapsule_Destructor"> <tt class="descname">PyCapsule_Destructor</tt><a class="headerlink" href="#PyCapsule_Destructor" title="Permalink to this definition">¶</a></dt> <dd><p>The type of a destructor callback for a capsule. Defined as:</p> <div class="highlight-c"><div class="highlight"><pre><span class="k">typedef</span> <span class="kt">void</span> <span class="p">(</span><span class="o">*</span><span class="n">PyCapsule_Destructor</span><span class="p">)(</span><span class="n">PyObject</span> <span class="o">*</span><span class="p">);</span> </pre></div> </div> <p>See <a class="reference internal" href="#PyCapsule_New" title="PyCapsule_New"><tt class="xref c c-func docutils literal"><span class="pre">PyCapsule_New()</span></tt></a> for the semantics of PyCapsule_Destructor callbacks.</p> </dd></dl> <dl class="function"> <dt id="PyCapsule_CheckExact"> int <tt class="descname">PyCapsule_CheckExact</tt><big>(</big><a class="reference internal" href="structures.html#PyObject" title="PyObject">PyObject</a><em> *p</em><big>)</big><a class="headerlink" href="#PyCapsule_CheckExact" title="Permalink to this definition">¶</a></dt> <dd><p>Return true if its argument is a <a class="reference internal" href="#PyCapsule" title="PyCapsule"><tt class="xref c c-type docutils literal"><span class="pre">PyCapsule</span></tt></a>.</p> </dd></dl> <dl class="function"> <dt id="PyCapsule_New"> <a class="reference internal" href="structures.html#PyObject" title="PyObject">PyObject</a>* <tt class="descname">PyCapsule_New</tt><big>(</big>void<em> *pointer</em>, const char<em> *name</em>, <a class="reference internal" href="#PyCapsule_Destructor" title="PyCapsule_Destructor">PyCapsule_Destructor</a><em> destructor</em><big>)</big><a class="headerlink" href="#PyCapsule_New" title="Permalink to this definition">¶</a></dt> <dd><em class="refcount">Return value: New reference.</em><p>Create a <a class="reference internal" href="#PyCapsule" title="PyCapsule"><tt class="xref c c-type docutils literal"><span class="pre">PyCapsule</span></tt></a> encapsulating the <em>pointer</em>. The <em>pointer</em> argument may not be <em>NULL</em>.</p> <p>On failure, set an exception and return <em>NULL</em>.</p> <p>The <em>name</em> string may either be <em>NULL</em> or a pointer to a valid C string. If non-<em>NULL</em>, this string must outlive the capsule. (Though it is permitted to free it inside the <em>destructor</em>.)</p> <p>If the <em>destructor</em> argument is not <em>NULL</em>, it will be called with the capsule as its argument when it is destroyed.</p> <p>If this capsule will be stored as an attribute of a module, the <em>name</em> should be specified as <tt class="docutils literal"><span class="pre">modulename.attributename</span></tt>. This will enable other modules to import the capsule using <a class="reference internal" href="#PyCapsule_Import" title="PyCapsule_Import"><tt class="xref c c-func docutils literal"><span class="pre">PyCapsule_Import()</span></tt></a>.</p> </dd></dl> <dl class="function"> <dt id="PyCapsule_GetPointer"> void* <tt class="descname">PyCapsule_GetPointer</tt><big>(</big><a class="reference internal" href="structures.html#PyObject" title="PyObject">PyObject</a><em> *capsule</em>, const char<em> *name</em><big>)</big><a class="headerlink" href="#PyCapsule_GetPointer" title="Permalink to this definition">¶</a></dt> <dd><p>Retrieve the <em>pointer</em> stored in the capsule. On failure, set an exception and return <em>NULL</em>.</p> <p>The <em>name</em> parameter must compare exactly to the name stored in the capsule. If the name stored in the capsule is <em>NULL</em>, the <em>name</em> passed in must also be <em>NULL</em>. Python uses the C function <tt class="xref c c-func docutils literal"><span class="pre">strcmp()</span></tt> to compare capsule names.</p> </dd></dl> <dl class="function"> <dt id="PyCapsule_GetDestructor"> <a class="reference internal" href="#PyCapsule_Destructor" title="PyCapsule_Destructor">PyCapsule_Destructor</a> <tt class="descname">PyCapsule_GetDestructor</tt><big>(</big><a class="reference internal" href="structures.html#PyObject" title="PyObject">PyObject</a><em> *capsule</em><big>)</big><a class="headerlink" href="#PyCapsule_GetDestructor" title="Permalink to this definition">¶</a></dt> <dd><p>Return the current destructor stored in the capsule. On failure, set an exception and return <em>NULL</em>.</p> <p>It is legal for a capsule to have a <em>NULL</em> destructor. This makes a <em>NULL</em> return code somewhat ambiguous; use <a class="reference internal" href="#PyCapsule_IsValid" title="PyCapsule_IsValid"><tt class="xref c c-func docutils literal"><span class="pre">PyCapsule_IsValid()</span></tt></a> or <a class="reference internal" href="exceptions.html#PyErr_Occurred" title="PyErr_Occurred"><tt class="xref c c-func docutils literal"><span class="pre">PyErr_Occurred()</span></tt></a> to disambiguate.</p> </dd></dl> <dl class="function"> <dt id="PyCapsule_GetContext"> void* <tt class="descname">PyCapsule_GetContext</tt><big>(</big><a class="reference internal" href="structures.html#PyObject" title="PyObject">PyObject</a><em> *capsule</em><big>)</big><a class="headerlink" href="#PyCapsule_GetContext" title="Permalink to this definition">¶</a></dt> <dd><p>Return the current context stored in the capsule. On failure, set an exception and return <em>NULL</em>.</p> <p>It is legal for a capsule to have a <em>NULL</em> context. This makes a <em>NULL</em> return code somewhat ambiguous; use <a class="reference internal" href="#PyCapsule_IsValid" title="PyCapsule_IsValid"><tt class="xref c c-func docutils literal"><span class="pre">PyCapsule_IsValid()</span></tt></a> or <a class="reference internal" href="exceptions.html#PyErr_Occurred" title="PyErr_Occurred"><tt class="xref c c-func docutils literal"><span class="pre">PyErr_Occurred()</span></tt></a> to disambiguate.</p> </dd></dl> <dl class="function"> <dt id="PyCapsule_GetName"> const char* <tt class="descname">PyCapsule_GetName</tt><big>(</big><a class="reference internal" href="structures.html#PyObject" title="PyObject">PyObject</a><em> *capsule</em><big>)</big><a class="headerlink" href="#PyCapsule_GetName" title="Permalink to this definition">¶</a></dt> <dd><p>Return the current name stored in the capsule. On failure, set an exception and return <em>NULL</em>.</p> <p>It is legal for a capsule to have a <em>NULL</em> name. This makes a <em>NULL</em> return code somewhat ambiguous; use <a class="reference internal" href="#PyCapsule_IsValid" title="PyCapsule_IsValid"><tt class="xref c c-func docutils literal"><span class="pre">PyCapsule_IsValid()</span></tt></a> or <a class="reference internal" href="exceptions.html#PyErr_Occurred" title="PyErr_Occurred"><tt class="xref c c-func docutils literal"><span class="pre">PyErr_Occurred()</span></tt></a> to disambiguate.</p> </dd></dl> <dl class="function"> <dt id="PyCapsule_Import"> void* <tt class="descname">PyCapsule_Import</tt><big>(</big>const char<em> *name</em>, int<em> no_block</em><big>)</big><a class="headerlink" href="#PyCapsule_Import" title="Permalink to this definition">¶</a></dt> <dd><p>Import a pointer to a C object from a capsule attribute in a module. The <em>name</em> parameter should specify the full name to the attribute, as in <tt class="docutils literal"><span class="pre">module.attribute</span></tt>. The <em>name</em> stored in the capsule must match this string exactly. If <em>no_block</em> is true, import the module without blocking (using <a class="reference internal" href="import.html#PyImport_ImportModuleNoBlock" title="PyImport_ImportModuleNoBlock"><tt class="xref c c-func docutils literal"><span class="pre">PyImport_ImportModuleNoBlock()</span></tt></a>). If <em>no_block</em> is false, import the module conventionally (using <a class="reference internal" href="import.html#PyImport_ImportModule" title="PyImport_ImportModule"><tt class="xref c c-func docutils literal"><span class="pre">PyImport_ImportModule()</span></tt></a>).</p> <p>Return the capsule’s internal <em>pointer</em> on success. On failure, set an exception and return <em>NULL</em>. However, if <a class="reference internal" href="#PyCapsule_Import" title="PyCapsule_Import"><tt class="xref c c-func docutils literal"><span class="pre">PyCapsule_Import()</span></tt></a> failed to import the module, and <em>no_block</em> was true, no exception is set.</p> </dd></dl> <dl class="function"> <dt id="PyCapsule_IsValid"> int <tt class="descname">PyCapsule_IsValid</tt><big>(</big><a class="reference internal" href="structures.html#PyObject" title="PyObject">PyObject</a><em> *capsule</em>, const char<em> *name</em><big>)</big><a class="headerlink" href="#PyCapsule_IsValid" title="Permalink to this definition">¶</a></dt> <dd><p>Determines whether or not <em>capsule</em> is a valid capsule. A valid capsule is non-<em>NULL</em>, passes <a class="reference internal" href="#PyCapsule_CheckExact" title="PyCapsule_CheckExact"><tt class="xref c c-func docutils literal"><span class="pre">PyCapsule_CheckExact()</span></tt></a>, has a non-<em>NULL</em> pointer stored in it, and its internal name matches the <em>name</em> parameter. (See <a class="reference internal" href="#PyCapsule_GetPointer" title="PyCapsule_GetPointer"><tt class="xref c c-func docutils literal"><span class="pre">PyCapsule_GetPointer()</span></tt></a> for information on how capsule names are compared.)</p> <p>In other words, if <a class="reference internal" href="#PyCapsule_IsValid" title="PyCapsule_IsValid"><tt class="xref c c-func docutils literal"><span class="pre">PyCapsule_IsValid()</span></tt></a> returns a true value, calls to any of the accessors (any function starting with <tt class="xref c c-func docutils literal"><span class="pre">PyCapsule_Get()</span></tt>) are guaranteed to succeed.</p> <p>Return a nonzero value if the object is valid and matches the name passed in. Return 0 otherwise. This function will not fail.</p> </dd></dl> <dl class="function"> <dt id="PyCapsule_SetContext"> int <tt class="descname">PyCapsule_SetContext</tt><big>(</big><a class="reference internal" href="structures.html#PyObject" title="PyObject">PyObject</a><em> *capsule</em>, void<em> *context</em><big>)</big><a class="headerlink" href="#PyCapsule_SetContext" title="Permalink to this definition">¶</a></dt> <dd><p>Set the context pointer inside <em>capsule</em> to <em>context</em>.</p> <p>Return 0 on success. Return nonzero and set an exception on failure.</p> </dd></dl> <dl class="function"> <dt id="PyCapsule_SetDestructor"> int <tt class="descname">PyCapsule_SetDestructor</tt><big>(</big><a class="reference internal" href="structures.html#PyObject" title="PyObject">PyObject</a><em> *capsule</em>, <a class="reference internal" href="#PyCapsule_Destructor" title="PyCapsule_Destructor">PyCapsule_Destructor</a><em> destructor</em><big>)</big><a class="headerlink" href="#PyCapsule_SetDestructor" title="Permalink to this definition">¶</a></dt> <dd><p>Set the destructor inside <em>capsule</em> to <em>destructor</em>.</p> <p>Return 0 on success. Return nonzero and set an exception on failure.</p> </dd></dl> <dl class="function"> <dt id="PyCapsule_SetName"> int <tt class="descname">PyCapsule_SetName</tt><big>(</big><a class="reference internal" href="structures.html#PyObject" title="PyObject">PyObject</a><em> *capsule</em>, const char<em> *name</em><big>)</big><a class="headerlink" href="#PyCapsule_SetName" title="Permalink to this definition">¶</a></dt> <dd><p>Set the name inside <em>capsule</em> to <em>name</em>. If non-<em>NULL</em>, the name must outlive the capsule. If the previous <em>name</em> stored in the capsule was not <em>NULL</em>, no attempt is made to free it.</p> <p>Return 0 on success. Return nonzero and set an exception on failure.</p> </dd></dl> <dl class="function"> <dt id="PyCapsule_SetPointer"> int <tt class="descname">PyCapsule_SetPointer</tt><big>(</big><a class="reference internal" href="structures.html#PyObject" title="PyObject">PyObject</a><em> *capsule</em>, void<em> *pointer</em><big>)</big><a class="headerlink" href="#PyCapsule_SetPointer" title="Permalink to this definition">¶</a></dt> <dd><p>Set the void pointer inside <em>capsule</em> to <em>pointer</em>. The pointer may not be <em>NULL</em>.</p> <p>Return 0 on success. Return nonzero and set an exception on failure.</p> </dd></dl> </div> </div> </div> </div> <div class="sphinxsidebar"> <div class="sphinxsidebarwrapper"> <h4>Previous topic</h4> <p class="topless"><a href="weakref.html" title="previous chapter">Weak Reference Objects</a></p> <h4>Next topic</h4> <p class="topless"><a href="cobject.html" title="next chapter">CObjects</a></p> <h3>This Page</h3> <ul class="this-page-menu"> <li><a href="../bugs.html">Report a Bug</a></li> <li><a href="../_sources/c-api/capsule.txt" rel="nofollow">Show Source</a></li> </ul> <div id="searchbox" style="display: none"> <h3>Quick search</h3> <form class="search" action="../search.html" method="get"> <input 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> <p class="searchtip" style="font-size: 90%"> Enter search terms or a module, class or function name. </p> </div> <script type="text/javascript">$('#searchbox').show(0);</script> </div> </div> <div class="clearer"></div> </div> <div class="related"> <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="cobject.html" title="CObjects" >next</a> |</li> <li class="right" > <a href="weakref.html" title="Weak Reference Objects" >previous</a> |</li> <li><img src="../_static/py.png" alt="" style="vertical-align: middle; margin-top: -1px"/></li> <li><a href="http://www.python.org/">Python</a> »</li> <li> <a href="../index.html">Python 2.7.5 documentation</a> » </li> <li><a href="index.html" >Python/C API Reference Manual</a> »</li> <li><a href="concrete.html" >Concrete Objects Layer</a> »</li> </ul> </div> <div class="footer"> © <a href="../copyright.html">Copyright</a> 1990-2020, Python Software Foundation. <br /> The Python Software Foundation is a non-profit corporation. <a href="http://www.python.org/psf/donations/">Please donate.</a> <br /> Last updated on Oct 13, 2020. <a href="../bugs.html">Found a bug</a>? <br /> Created using <a href="http://sphinx.pocoo.org/">Sphinx</a> 1.1.3. </div> </body> </html>