Python314/Doc/html/c-api/refcounting.html - master - shapovalovav/AI-Agent

Python314/Doc/html/c-api/refcounting.html
559 строк40 KB
Anatoly1147
first_commit
11 июл 2026, 17:02
11 июл 2026, 17:02f6c78bd
<!DOCTYPE html>

<html lang="en" data-content_root="../">
  <head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" /><meta name="viewport" content="width=device-width, initial-scale=1" />
<meta property="og:title" content="Reference Counting" />
<meta property="og:type" content="website" />
<meta property="og:url" content="https://docs.python.org/3/c-api/refcounting.html" />
<meta property="og:site_name" content="Python documentation" />
<meta property="og:description" content="The functions and macros in this section are used for managing reference counts of Python objects." />
<meta property="og:image" content="_static/og-image.png" />
<meta property="og:image:alt" content="Python documentation" />
<meta name="description" content="The functions and macros in this section are used for managing reference counts of Python objects." />
<meta name="theme-color" content="#3776ab">
<meta property="og:image:width" content="200">
<meta property="og:image:height" content="200">

    <title>Reference Counting &#8212; Python 3.14.4 documentation</title><meta name="viewport" content="width=device-width, initial-scale=1.0">
    
    <link rel="stylesheet" type="text/css" href="../_static/pygments.css?v=b86133f3" />
    <link rel="stylesheet" type="text/css" href="../_static/classic.css?v=234b1a7c" />
    <link rel="stylesheet" type="text/css" href="../_static/pydoctheme.css?v=82640b3f" />
    <link id="pygments_dark_css" media="(prefers-color-scheme: dark)" rel="stylesheet" type="text/css" href="../_static/pygments_dark.css?v=5349f25f" />
    
    <script src="../_static/documentation_options.js?v=1885ab2e"></script>
    <script src="../_static/doctools.js?v=9bcbadda"></script>
    <script src="../_static/sphinx_highlight.js?v=dc90522c"></script>
    
    <script src="../_static/sidebar.js"></script>
    
    <link rel="search" type="application/opensearchdescription+xml"
          title="Search within Python 3.14.4 documentation"
          href="../_static/opensearch.xml"/>
    <link rel="author" title="About these documents" href="../about.html" />
    <link rel="index" title="Index" href="../genindex.html" />
    <link rel="search" title="Search" href="../search.html" />
    <link rel="copyright" title="Copyright" href="../copyright.html" />
    <link rel="next" title="Exception Handling" href="exceptions.html" />
    <link rel="prev" title="The Very High Level Layer" href="veryhigh.html" />
    
      
      <link rel="canonical" href="https://docs.python.org/3/c-api/refcounting.html">
      
    

    
    <style>
      @media only screen {
        table.full-width-table {
            width: 100%;
        }
      }
    </style>
<link rel="stylesheet" href="../_static/pydoctheme_dark.css" media="(prefers-color-scheme: dark)" id="pydoctheme_dark_css">
    <link rel="shortcut icon" type="image/png" href="../_static/py.svg">
            <script type="text/javascript" src="../_static/copybutton.js"></script>
            <script type="text/javascript" src="../_static/menu.js"></script>
            <script type="text/javascript" src="../_static/search-focus.js"></script>
            <script type="text/javascript" src="../_static/themetoggle.js"></script> 
            <script type="text/javascript" src="../_static/rtd_switcher.js"></script>
            <meta name="readthedocs-addons-api-version" content="1">

  </head>
<body>
<div class="mobile-nav">
    <input type="checkbox" id="menuToggler" class="toggler__input" aria-controls="navigation"
           aria-pressed="false" aria-expanded="false" role="button" aria-label="Menu">
    <nav class="nav-content" role="navigation">
        <label for="menuToggler" class="toggler__label">
            <span></span>
        </label>
        <span class="nav-items-wrapper">
            <a href="https://www.python.org/" class="nav-logo">
                <img src="../_static/py.svg" alt="Python logo">
            </a>
            <span class="version_switcher_placeholder"></span>
            <form role="search" class="search" action="../search.html" method="get">
                <svg xmlns="http://www.w3.org/2000/svg" width="20" height="20" viewBox="0 0 24 24" class="search-icon">
                    <path fill-rule="nonzero" fill="currentColor" d="M15.5 14h-.79l-.28-.27a6.5 6.5 0 001.48-5.34c-.47-2.78-2.79-5-5.59-5.34a6.505 6.505 0 00-7.27 7.27c.34 2.8 2.56 5.12 5.34 5.59a6.5 6.5 0 005.34-1.48l.27.28v.79l4.25 4.25c.41.41 1.08.41 1.49 0 .41-.41.41-1.08 0-1.49L15.5 14zm-6 0C7.01 14 5 11.99 5 9.5S7.01 5 9.5 5 14 7.01 14 9.5 11.99 14 9.5 14z"></path>
                </svg>
                <input placeholder="Quick search" aria-label="Quick search" type="search" name="q">
                <input type="submit" value="Go">
            </form>
        </span>
    </nav>
    <div class="menu-wrapper">
        <nav class="menu" role="navigation" aria-label="main navigation">
            <div class="language_switcher_placeholder"></div>
            
<label class="theme-selector-label">
    Theme
    <select class="theme-selector" oninput="activateTheme(this.value)">
        <option value="auto" selected>Auto</option>
        <option value="light">Light</option>
        <option value="dark">Dark</option>
    </select>
</label>
  <div>
    <h4>Previous topic</h4>
    <p class="topless"><a href="veryhigh.html"
                          title="previous chapter">The Very High Level Layer</a></p>
  </div>
  <div>
    <h4>Next topic</h4>
    <p class="topless"><a href="exceptions.html"
                          title="next chapter">Exception Handling</a></p>
  </div>
  <script>
    document.addEventListener('DOMContentLoaded', () => {
        const title = document.querySelector('meta[property="og:title"]').content;
        const elements = document.querySelectorAll('.improvepage');
        const pageurl = window.location.href.split('?')[0];
        elements.forEach(element => {
            const url = new URL(element.href.split('?')[0].replace("-nojs", ""));
            url.searchParams.set('pagetitle', title);
            url.searchParams.set('pageurl', pageurl);
            url.searchParams.set('pagesource', "c-api/refcounting.rst");
            element.href = url.toString();
        });
    });
  </script>
  <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 class="improvepage" href="../improve-page-nojs.html">Improve this page</a></li>
      <li>
        <a href="https://github.com/python/cpython/blob/main/Doc/c-api/refcounting.rst?plain=1"
            rel="nofollow">Show source
        </a>
      </li>
      
    </ul>
  </div>
        </nav>
    </div>
</div>

  
    <div class="related" role="navigation" aria-label="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="exceptions.html" title="Exception Handling"
             accesskey="N">next</a> |</li>
        <li class="right" >
          <a href="veryhigh.html" title="The Very High Level Layer"
             accesskey="P">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> &#187;</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">3.14.4 Documentation</a> &#187;
    </li>

          <li class="nav-item nav-item-1"><a href="index.html" accesskey="U">Python/C API reference manual</a> &#187;</li>
        <li class="nav-item nav-item-this"><a href="">Reference Counting</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="search" name="q" id="search-box">
          <input type="submit" value="Go">
        </form>
    </div>
                     |
                </li>
            <li class="right">
<label class="theme-selector-label">
    Theme
    <select class="theme-selector" oninput="activateTheme(this.value)">
        <option value="auto" selected>Auto</option>
        <option value="light">Light</option>
        <option value="dark">Dark</option>
    </select>
</label> |</li>
            
      </ul>
    </div>    

    <div class="document">
      <div class="documentwrapper">
        <div class="bodywrapper">
          <div class="body" role="main">
            
  <section id="reference-counting">
<span id="countingrefs"></span><h1>Reference Counting<a class="headerlink" href="#reference-counting" title="Link to this heading">¶</a></h1>
<p>The functions and macros in this section are used for managing reference counts
of Python objects.</p>
<dl class="c function">
<dt class="sig sig-object c" id="c.Py_REFCNT">
<a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><span class="n"><span class="pre">Py_ssize_t</span></span></a><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_REFCNT</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">o</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_REFCNT" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.14.</em><p>Get the reference count of the Python object <em>o</em>.</p>
<p>Note that the returned value may not actually reflect how many
references to the object are actually held.  For example, some
objects are <a class="reference internal" href="../glossary.html#term-immortal"><span class="xref std std-term">immortal</span></a> and have a very high refcount that does not
reflect the actual number of references.  Consequently, do not rely
on the returned value to be accurate, other than a value of 0 or 1.</p>
<p>Use the <a class="reference internal" href="#c.Py_SET_REFCNT" title="Py_SET_REFCNT"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_SET_REFCNT()</span></code></a> function to set an object reference count.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>On <a class="reference internal" href="../glossary.html#term-free-threaded-build"><span class="xref std std-term">free-threaded builds</span></a> of Python, returning 1
isn’t sufficient to determine if it’s safe to treat <em>o</em> as having no
access by other threads. Use <a class="reference internal" href="object.html#c.PyUnstable_Object_IsUniquelyReferenced" title="PyUnstable_Object_IsUniquelyReferenced"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnstable_Object_IsUniquelyReferenced()</span></code></a>
for that instead.</p>
<p>See also the function <a class="reference internal" href="object.html#c.PyUnstable_Object_IsUniqueReferencedTemporary" title="PyUnstable_Object_IsUniqueReferencedTemporary"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnstable_Object_IsUniqueReferencedTemporary()</span></code></a>.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.10: </span><a class="reference internal" href="#c.Py_REFCNT" title="Py_REFCNT"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_REFCNT()</span></code></a> is changed to the inline static function.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.11: </span>The parameter type is no longer <span class="c-expr sig sig-inline c"><span class="k">const</span><span class="w"> </span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n">PyObject</span></a><span class="p">*</span></span>.</p>
</div>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.Py_SET_REFCNT">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_SET_REFCNT</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">o</span></span>, <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><span class="n"><span class="pre">Py_ssize_t</span></span></a><span class="w"> </span><span class="n"><span class="pre">refcnt</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_SET_REFCNT" title="Link to this definition">¶</a><br /></dt>
<dd><p>Set the object <em>o</em> reference counter to <em>refcnt</em>.</p>
<p>On <a class="reference internal" href="../using/configure.html#free-threading-build"><span class="std std-ref">Python build with Free Threading</span></a>, if
<em>refcnt</em> is larger than <code class="docutils literal notranslate"><span class="pre">UINT32_MAX</span></code>, the object is made <a class="reference internal" href="../glossary.html#term-immortal"><span class="xref std std-term">immortal</span></a>.</p>
<p>This function has no effect on <a class="reference internal" href="../glossary.html#term-immortal"><span class="xref std std-term">immortal</span></a> objects.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.9.</span></p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.12: </span>Immortal objects are not modified.</p>
</div>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.Py_INCREF">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_INCREF</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">o</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_INCREF" title="Link to this definition">¶</a><br /></dt>
<dd><p>Indicate taking a new <a class="reference internal" href="../glossary.html#term-strong-reference"><span class="xref std std-term">strong reference</span></a> to object <em>o</em>,
indicating it is in use and should not be destroyed.</p>
<p>This function has no effect on <a class="reference internal" href="../glossary.html#term-immortal"><span class="xref std std-term">immortal</span></a> objects.</p>
<p>This function is usually used to convert a <a class="reference internal" href="../glossary.html#term-borrowed-reference"><span class="xref std std-term">borrowed reference</span></a> to a
<a class="reference internal" href="../glossary.html#term-strong-reference"><span class="xref std std-term">strong reference</span></a> in-place. The <a class="reference internal" href="#c.Py_NewRef" title="Py_NewRef"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_NewRef()</span></code></a> function can be
used to create a new <span class="xref std std-term">strong reference</span>.</p>
<p>When done using the object, release is by calling <a class="reference internal" href="#c.Py_DECREF" title="Py_DECREF"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_DECREF()</span></code></a>.</p>
<p>The object must not be <code class="docutils literal notranslate"><span class="pre">NULL</span></code>; if you aren’t sure that it isn’t
<code class="docutils literal notranslate"><span class="pre">NULL</span></code>, use <a class="reference internal" href="#c.Py_XINCREF" title="Py_XINCREF"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_XINCREF()</span></code></a>.</p>
<p>Do not expect this function to actually modify <em>o</em> in any way.
For at least <span class="target" id="index-0"></span><a class="pep reference external" href="https://peps.python.org/pep-0683/"><strong>some objects</strong></a>,
this function has no effect.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.12: </span>Immortal objects are not modified.</p>
</div>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.Py_XINCREF">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_XINCREF</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">o</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_XINCREF" title="Link to this definition">¶</a><br /></dt>
<dd><p>Similar to <a class="reference internal" href="#c.Py_INCREF" title="Py_INCREF"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_INCREF()</span></code></a>, but the object <em>o</em> can be <code class="docutils literal notranslate"><span class="pre">NULL</span></code>,
in which case this has no effect.</p>
<p>See also <a class="reference internal" href="#c.Py_XNewRef" title="Py_XNewRef"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_XNewRef()</span></code></a>.</p>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.Py_NewRef">
<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_NewRef</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">o</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_NewRef" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.10.</em><p>Create a new <a class="reference internal" href="../glossary.html#term-strong-reference"><span class="xref std std-term">strong reference</span></a> to an object:
call <a class="reference internal" href="#c.Py_INCREF" title="Py_INCREF"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_INCREF()</span></code></a> on <em>o</em> and return the object <em>o</em>.</p>
<p>When the <a class="reference internal" href="../glossary.html#term-strong-reference"><span class="xref std std-term">strong reference</span></a> is no longer needed, <a class="reference internal" href="#c.Py_DECREF" title="Py_DECREF"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_DECREF()</span></code></a>
should be called on it to release the reference.</p>
<p>The object <em>o</em> must not be <code class="docutils literal notranslate"><span class="pre">NULL</span></code>; use <a class="reference internal" href="#c.Py_XNewRef" title="Py_XNewRef"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_XNewRef()</span></code></a> if <em>o</em> can be
<code class="docutils literal notranslate"><span class="pre">NULL</span></code>.</p>
<p>For example:</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="n">Py_INCREF</span><span class="p">(</span><span class="n">obj</span><span class="p">);</span>
<span class="n">self</span><span class="o">-&gt;</span><span class="n">attr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">obj</span><span class="p">;</span>
</pre></div>
</div>
<p>can be written as:</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="n">self</span><span class="o">-&gt;</span><span class="n">attr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Py_NewRef</span><span class="p">(</span><span class="n">obj</span><span class="p">);</span>
</pre></div>
</div>
<p>See also <a class="reference internal" href="#c.Py_INCREF" title="Py_INCREF"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_INCREF()</span></code></a>.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.10.</span></p>
</div>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.Py_XNewRef">
<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_XNewRef</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">o</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_XNewRef" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.10.</em><p>Similar to <a class="reference internal" href="#c.Py_NewRef" title="Py_NewRef"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_NewRef()</span></code></a>, but the object <em>o</em> can be NULL.</p>
<p>If the object <em>o</em> is <code class="docutils literal notranslate"><span class="pre">NULL</span></code>, the function just returns <code class="docutils literal notranslate"><span class="pre">NULL</span></code>.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.10.</span></p>
</div>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.Py_DECREF">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_DECREF</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">o</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_DECREF" title="Link to this definition">¶</a><br /></dt>
<dd><p>Release a <a class="reference internal" href="../glossary.html#term-strong-reference"><span class="xref std std-term">strong reference</span></a> to object <em>o</em>, indicating the
reference is no longer used.</p>
<p>This function has no effect on <a class="reference internal" href="../glossary.html#term-immortal"><span class="xref std std-term">immortal</span></a> objects.</p>
<p>Once the last <a class="reference internal" href="../glossary.html#term-strong-reference"><span class="xref std std-term">strong reference</span></a> is released
(i.e. the object’s reference count reaches 0),
the object’s type’s deallocation
function (which must not be <code class="docutils literal notranslate"><span class="pre">NULL</span></code>) is invoked.</p>
<p>This function is usually used to delete a <a class="reference internal" href="../glossary.html#term-strong-reference"><span class="xref std std-term">strong reference</span></a> before
exiting its scope.</p>
<p>The object must not be <code class="docutils literal notranslate"><span class="pre">NULL</span></code>; if you aren’t sure that it isn’t <code class="docutils literal notranslate"><span class="pre">NULL</span></code>,
use <a class="reference internal" href="#c.Py_XDECREF" title="Py_XDECREF"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_XDECREF()</span></code></a>.</p>
<p>Do not expect this function to actually modify <em>o</em> in any way.
For at least <span class="target" id="index-1"></span><a class="pep reference external" href="https://peps.python.org/pep-0683/"><strong>some objects</strong></a>,
this function has no effect.</p>
<div class="admonition warning">
<p class="admonition-title">Warning</p>
<p>The deallocation function can cause arbitrary Python code to be invoked (e.g.
when a class instance with a <a class="reference internal" href="../reference/datamodel.html#object.__del__" title="object.__del__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__del__()</span></code></a> method is deallocated).  While
exceptions in such code are not propagated, the executed code has free access to
all Python global variables.  This means that any object that is reachable from
a global variable should be in a consistent state before <a class="reference internal" href="#c.Py_DECREF" title="Py_DECREF"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_DECREF()</span></code></a> is
invoked.  For example, code to delete an object from a list should copy a
reference to the deleted object in a temporary variable, update the list data
structure, and then call <code class="xref c c-func docutils literal notranslate"><span class="pre">Py_DECREF()</span></code> for the temporary variable.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.12: </span>Immortal objects are not modified.</p>
</div>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.Py_XDECREF">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_XDECREF</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">o</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_XDECREF" title="Link to this definition">¶</a><br /></dt>
<dd><p>Similar to <a class="reference internal" href="#c.Py_DECREF" title="Py_DECREF"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_DECREF()</span></code></a>, but the object <em>o</em> can be <code class="docutils literal notranslate"><span class="pre">NULL</span></code>,
in which case this has no effect.
The same warning from <code class="xref c c-func docutils literal notranslate"><span class="pre">Py_DECREF()</span></code> applies here as well.</p>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.Py_CLEAR">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_CLEAR</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">o</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_CLEAR" title="Link to this definition">¶</a><br /></dt>
<dd><p>Release a <a class="reference internal" href="../glossary.html#term-strong-reference"><span class="xref std std-term">strong reference</span></a> for object <em>o</em>.
The object may be <code class="docutils literal notranslate"><span class="pre">NULL</span></code>, in
which case the macro has no effect; otherwise the effect is the same as for
<a class="reference internal" href="#c.Py_DECREF" title="Py_DECREF"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_DECREF()</span></code></a>, except that the argument is also set to <code class="docutils literal notranslate"><span class="pre">NULL</span></code>.  The warning
for <code class="xref c c-func docutils literal notranslate"><span class="pre">Py_DECREF()</span></code> does not apply with respect to the object passed because
the macro carefully uses a temporary variable and sets the argument to <code class="docutils literal notranslate"><span class="pre">NULL</span></code>
before releasing the reference.</p>
<p>It is a good idea to use this macro whenever releasing a reference
to an object that might be traversed during garbage collection.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.12: </span>The macro argument is now only evaluated once. If the argument has side
effects, these are no longer duplicated.</p>
</div>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.Py_IncRef">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_IncRef</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">o</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_IncRef" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Indicate taking a new <a class="reference internal" href="../glossary.html#term-strong-reference"><span class="xref std std-term">strong reference</span></a> to object <em>o</em>.
A function version of <a class="reference internal" href="#c.Py_XINCREF" title="Py_XINCREF"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_XINCREF()</span></code></a>.
It can be used for runtime dynamic embedding of Python.</p>
</dd></dl>

<dl class="c function">
<dt class="sig sig-object c" id="c.Py_DecRef">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_DecRef</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">o</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_DecRef" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Release a <a class="reference internal" href="../glossary.html#term-strong-reference"><span class="xref std std-term">strong reference</span></a> to object <em>o</em>.
A function version of <a class="reference internal" href="#c.Py_XDECREF" title="Py_XDECREF"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_XDECREF()</span></code></a>.
It can be used for runtime dynamic embedding of Python.</p>
</dd></dl>

<dl class="c macro">
<dt class="sig sig-object c" id="c.Py_SETREF">
<span class="sig-name descname"><span class="n"><span class="pre">Py_SETREF</span></span></span><span class="sig-paren">(</span><span class="n"><span class="pre">dst</span></span>, <span class="n"><span class="pre">src</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_SETREF" title="Link to this definition">¶</a><br /></dt>
<dd><p>Macro safely releasing a <a class="reference internal" href="../glossary.html#term-strong-reference"><span class="xref std std-term">strong reference</span></a> to object <em>dst</em>
and setting <em>dst</em> to <em>src</em>.</p>
<p>As in case of <a class="reference internal" href="#c.Py_CLEAR" title="Py_CLEAR"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_CLEAR()</span></code></a>, “the obvious” code can be deadly:</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="n">Py_DECREF</span><span class="p">(</span><span class="n">dst</span><span class="p">);</span>
<span class="n">dst</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">src</span><span class="p">;</span>
</pre></div>
</div>
<p>The safe way is:</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="n">Py_SETREF</span><span class="p">(</span><span class="n">dst</span><span class="p">,</span><span class="w"> </span><span class="n">src</span><span class="p">);</span>
</pre></div>
</div>
<p>That arranges to set <em>dst</em> to <em>src</em> <em>before</em> releasing the reference
to the old value of <em>dst</em>, so that any code triggered as a side-effect
of <em>dst</em> getting torn down no longer believes <em>dst</em> points
to a valid object.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.6.</span></p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.12: </span>The macro arguments are now only evaluated once. If an argument has side
effects, these are no longer duplicated.</p>
</div>
</dd></dl>

<dl class="c macro">
<dt class="sig sig-object c" id="c.Py_XSETREF">
<span class="sig-name descname"><span class="n"><span class="pre">Py_XSETREF</span></span></span><span class="sig-paren">(</span><span class="n"><span class="pre">dst</span></span>, <span class="n"><span class="pre">src</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.Py_XSETREF" title="Link to this definition">¶</a><br /></dt>
<dd><p>Variant of <a class="reference internal" href="#c.Py_SETREF" title="Py_SETREF"><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_SETREF</span></code></a> macro that uses <a class="reference internal" href="#c.Py_XDECREF" title="Py_XDECREF"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_XDECREF()</span></code></a> instead
of <a class="reference internal" href="#c.Py_DECREF" title="Py_DECREF"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_DECREF()</span></code></a>.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.6.</span></p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.12: </span>The macro arguments are now only evaluated once. If an argument has side
effects, these are no longer duplicated.</p>
</div>
</dd></dl>

</section>


            <div class="clearer"></div>
          </div>
        </div>
      </div>
      <div class="sphinxsidebar" role="navigation" aria-label="Main">
        <div class="sphinxsidebarwrapper">
  <div>
    <h4>Previous topic</h4>
    <p class="topless"><a href="veryhigh.html"
                          title="previous chapter">The Very High Level Layer</a></p>
  </div>
  <div>
    <h4>Next topic</h4>
    <p class="topless"><a href="exceptions.html"
                          title="next chapter">Exception Handling</a></p>
  </div>
  <script>
    document.addEventListener('DOMContentLoaded', () => {
        const title = document.querySelector('meta[property="og:title"]').content;
        const elements = document.querySelectorAll('.improvepage');
        const pageurl = window.location.href.split('?')[0];
        elements.forEach(element => {
            const url = new URL(element.href.split('?')[0].replace("-nojs", ""));
            url.searchParams.set('pagetitle', title);
            url.searchParams.set('pageurl', pageurl);
            url.searchParams.set('pagesource', "c-api/refcounting.rst");
            element.href = url.toString();
        });
    });
  </script>
  <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 class="improvepage" href="../improve-page-nojs.html">Improve this page</a></li>
      <li>
        <a href="https://github.com/python/cpython/blob/main/Doc/c-api/refcounting.rst?plain=1"
            rel="nofollow">Show source
        </a>
      </li>
      
    </ul>
  </div>
        </div>
<div id="sidebarbutton" title="Collapse sidebar">
<span>«</span>
</div>

      </div>
      <div class="clearer"></div>
    </div>  
    <div class="related" role="navigation" aria-label="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="exceptions.html" title="Exception Handling"
             >next</a> |</li>
        <li class="right" >
          <a href="veryhigh.html" title="The Very High Level Layer"
             >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> &#187;</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">3.14.4 Documentation</a> &#187;
    </li>

          <li class="nav-item nav-item-1"><a href="index.html" >Python/C API reference manual</a> &#187;</li>
        <li class="nav-item nav-item-this"><a href="">Reference Counting</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="search" name="q" id="search-box">
          <input type="submit" value="Go">
        </form>
    </div>
                     |
                </li>
            <li class="right">
<label class="theme-selector-label">
    Theme
    <select class="theme-selector" oninput="activateTheme(this.value)">
        <option value="auto" selected>Auto</option>
        <option value="light">Light</option>
        <option value="dark">Dark</option>
    </select>
</label> |</li>
            
      </ul>
    </div>  
    <div class="footer">
    &copy; <a href="../copyright.html">Copyright</a> 2001 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 Apr 07, 2026 (13:52 UTC).
    
      <a href="/bugs.html">Found a bug</a>?
    
    <br>

    Created using <a href="https://www.sphinx-doc.org/">Sphinx</a> 8.2.3.
    </div>

  </body>
</html>