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<section id="reference-counting">
<span id="countingrefs"></span><h1>參照計數<a class="headerlink" href="#reference-counting" title="連結到這個標頭">¶</a></h1>
<p>本節中的函式與巨集用於管理 Python 物件的參照計數。</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="連結到這個定義">¶</a><br /></dt>
<dd><em class="stableabi"> 為 <a class="reference internal" href="stable.html#stable"><span class="std std-ref">穩定 ABI 的一部分</span></a> 自 3.14 版本開始.</em><p>取得物件 <em>o</em> 的參照計數。</p>
<p>請注意，回傳的值可能實際上並不反映實際保存了多少對該物件的參照。例如，某些物件是「<a class="reference internal" href="../glossary.html#term-immortal"><span class="xref std std-term">不滅的 (immortal)</span></a>」，並且具有非常高的參照計數，不能反映實際的參照數量。因此，除了 0 或 1 以外，不要依賴回傳值的準確性。</p>
<p>使用 <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> 函式設定物件參照計數。</p>
<div class="admonition note">
<p class="admonition-title">備註</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">在 3.10 版的變更: </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> 更改為行內靜態函式 (inline static function)。</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">在 3.11 版的變更: </span>參數型別不再是 <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="連結到這個定義">¶</a><br /></dt>
<dd><p>設定物件 <em>o</em> 的參照計數。</p>
<p>在<a class="reference internal" href="../using/configure.html#free-threading-build"><span class="std std-ref">啟用自由執行緒的 Python 建置</span></a>中，如果 <em>refcnt</em> 大於 <code class="docutils literal notranslate"><span class="pre">UINT32_MAX</span></code>，則該物件會被設為<a class="reference internal" href="../glossary.html#term-immortal"><span class="xref std std-term">不滅的 (immortal)</span></a>。</p>
<p>請注意，此函式對<a class="reference internal" href="../glossary.html#term-immortal"><span class="xref std std-term">不滅的</span></a>物件沒有影響。</p>
<div class="versionadded">
<p><span class="versionmodified added">在 3.9 版被加入.</span></p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">在 3.12 版的變更: </span>不滅的物件不會被修改。</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="連結到這個定義">¶</a><br /></dt>
<dd><p>代表取得對於物件 <em>o</em> 的新<a class="reference internal" href="../glossary.html#term-strong-reference"><span class="xref std std-term">強參照</span></a>，即它正在使用且不應被銷毀。</p>
<p>請注意，此函式對<a class="reference internal" href="../glossary.html#term-immortal"><span class="xref std std-term">不滅的</span></a>物件沒有影響。</p>
<p>此函式通常用於將<a class="reference internal" href="../glossary.html#term-borrowed-reference"><span class="xref std std-term">借用參照</span></a>原地 (in-place) 轉換為<a class="reference internal" href="../glossary.html#term-strong-reference"><span class="xref std std-term">強參照</span></a>。<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> 函式可用於建立新的<a class="reference internal" href="../glossary.html#term-strong-reference"><span class="xref std std-term">強參照</span></a>。</p>
<p>使用完該物件後，透過呼叫 <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> 來釋放它。</p>
<p>該物件不能為 <code class="docutils literal notranslate"><span class="pre">NULL</span></code>；如果你不確定它不是 <code class="docutils literal notranslate"><span class="pre">NULL</span></code>，請使用 <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>不要期望此函式會以任何方式實際修改 <em>o</em>，至少對於<span class="target" id="index-4"></span><a class="pep reference external" href="https://peps.python.org/pep-0683/"><strong>某些物件</strong></a>來說，此函式沒有任何效果。</p>
<div class="versionchanged">
<p><span class="versionmodified changed">在 3.12 版的變更: </span>不滅的物件不會被修改。</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="連結到這個定義">¶</a><br /></dt>
<dd><p>與 <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> 類似，但物件 <em>o</em> 可以為 <code class="docutils literal notranslate"><span class="pre">NULL</span></code>，在這種情況下這就不會有任何效果。</p>
<p>另請見 <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="連結到這個定義">¶</a><br /></dt>
<dd><em class="stableabi"> 為 <a class="reference internal" href="stable.html#stable"><span class="std std-ref">穩定 ABI 的一部分</span></a> 自 3.10 版本開始.</em><p>建立對物件的新<a class="reference internal" href="../glossary.html#term-strong-reference"><span class="xref std std-term">強參照</span></a>：於 <em>o</em> 呼叫 <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> 並回傳物件 <em>o</em>。</p>
<p>當不再需要<a class="reference internal" href="../glossary.html#term-strong-reference"><span class="xref std std-term">強參照</span></a>時，應對其呼叫 <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> 以釋放該參照。</p>
<p>物件 <em>o</em> 不能為 <code class="docutils literal notranslate"><span class="pre">NULL</span></code>；如果 <em>o</em> 可以為 <code class="docutils literal notranslate"><span class="pre">NULL</span></code>，則使用 <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>
<p>舉例來說：</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">-></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>可以寫成：</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="n">self</span><span class="o">-></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>另請參閱 <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">在 3.10 版被加入.</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="連結到這個定義">¶</a><br /></dt>
<dd><em class="stableabi"> 為 <a class="reference internal" href="stable.html#stable"><span class="std std-ref">穩定 ABI 的一部分</span></a> 自 3.10 版本開始.</em><p>與 <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> 類似，但物件 <em>o</em> 可以為 NULL。</p>
<p>如果物件 <em>o</em> 為 <code class="docutils literal notranslate"><span class="pre">NULL</span></code>，則該函式僅回傳 <code class="docutils literal notranslate"><span class="pre">NULL</span></code>。</p>
<div class="versionadded">
<p><span class="versionmodified added">在 3.10 版被加入.</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="連結到這個定義">¶</a><br /></dt>
<dd><p>釋放一個對物件 <em>o</em> 的<a class="reference internal" href="../glossary.html#term-strong-reference"><span class="xref std std-term">強參照</span></a>，代表該參照不會再被使用。</p>
<p>請注意，此函式對<a class="reference internal" href="../glossary.html#term-immortal"><span class="xref std std-term">不滅的</span></a>物件沒有影響。</p>
<p>如果最後一個<a class="reference internal" href="../glossary.html#term-strong-reference"><span class="xref std std-term">強參照</span></a>被釋放（即物件的參照計數達到零），則觸發物件之型別的釋放函式 (deallocation function)（不得為 <code class="docutils literal notranslate"><span class="pre">NULL</span></code>）。</p>
<p>此函式通常用於在退出作用域之前刪除<a class="reference internal" href="../glossary.html#term-strong-reference"><span class="xref std std-term">強參照</span></a>。</p>
<p>該物件不能為 <code class="docutils literal notranslate"><span class="pre">NULL</span></code>；如果你不確定它不是 <code class="docutils literal notranslate"><span class="pre">NULL</span></code>，請改用 <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>不要期望此函式會以任何方式實際修改 <em>o</em>，至少對於<span class="target" id="index-5"></span><a class="pep reference external" href="https://peps.python.org/pep-0683/"><strong>某些物件</strong></a>來說，此函式沒有任何效果。</p>
<div class="admonition warning">
<p class="admonition-title">警告</p>
<p>釋放函式可以導致任意 Python 程式碼被叫用（例如，當釋放具有 <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> 方法的類別實例時）。雖然此類程式碼中的例外不會被傳遞出來，但執行的程式碼可以自由存取所有 Python 全域變數。這意味著在叫用 <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> 之前，可從全域變數存取的任何物件都應處於一致狀態。例如，從 list 中刪除物件的程式碼應將已刪除物件的參照複製到臨時變數中，更新 list 資料結構，然後為臨時變數呼叫 <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>
<div class="versionchanged">
<p><span class="versionmodified changed">在 3.12 版的變更: </span>不滅的物件不會被修改。</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="連結到這個定義">¶</a><br /></dt>
<dd><p>和 <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> 類似，但該物件可以是 <code class="docutils literal notranslate"><span class="pre">NULL</span></code>，在這種情況下巨集不起作用。在這裡也會出現與 <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> 相同的警告。</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="連結到這個定義">¶</a><br /></dt>
<dd><p>釋放對於物件 <em>o</em> 的<a class="reference internal" href="../glossary.html#term-strong-reference"><span class="xref std std-term">強參照</span></a>。該物件可能是 <code class="docutils literal notranslate"><span class="pre">NULL</span></code>，在這種情況下巨集不起作用；否則，效果與 <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> 相同，除非引數也設定為 <code class="docutils literal notranslate"><span class="pre">NULL</span></code>。<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> 的警告不適用於傳遞的物件，因為巨集在釋放其參照之前小心地使用臨時變數並將引數設定為 <code class="docutils literal notranslate"><span class="pre">NULL</span></code>。</p>
<p>每當要釋放垃圾回收 (garbage collection) 期間可能被遍歷到之對於物件的參照時，使用此巨集是個好主意。</p>
<div class="versionchanged">
<p><span class="versionmodified changed">在 3.12 版的變更: </span>巨集引數現在僅會被求值 (evaluate) 一次。如果引數有其他副作用，則不再重複作用。</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="連結到這個定義">¶</a><br /></dt>
<dd><em class="stableabi"> 為 <a class="reference internal" href="stable.html#stable"><span class="std std-ref">穩定 ABI 的一部分</span></a>.</em><p>代表取得對於物件 <em>o</em> 的<a class="reference internal" href="../glossary.html#term-strong-reference"><span class="xref std std-term">強參照</span></a>。<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> 的函式版本。它可用於 Python 的 runtime 動態嵌入。</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="連結到這個定義">¶</a><br /></dt>
<dd><em class="stableabi"> 為 <a class="reference internal" href="stable.html#stable"><span class="std std-ref">穩定 ABI 的一部分</span></a>.</em><p>釋放對物件 <em>o</em> 的<a class="reference internal" href="../glossary.html#term-strong-reference"><span class="xref std std-term">強參照</span></a>。<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> 的函式版本。它可用於 Python 的 runtime 動態嵌入。</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="連結到這個定義">¶</a><br /></dt>
<dd><p>巨集安全地釋放對於物件 <em>dst</em> 的<a class="reference internal" href="../glossary.html#term-strong-reference"><span class="xref std std-term">強參照</span></a>並將 <em>dst</em> 設定為 <em>src</em>。</p>
<p>與 <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> 的情況一樣，「明顯的」程式碼可能是致命的：</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>安全的方法是：</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>這會在釋放對 <em>dst</em> 舊值的參照<em>之前</em>將 <em>dst</em> 設定為 <em>src</em>，使得因 <em>dst</em> 被拆除而觸發的任何副作用 (side-effect) 之程式碼不會相信 <em>dst</em> 是指向一個有效物件。</p>
<div class="versionadded">
<p><span class="versionmodified added">在 3.6 版被加入.</span></p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">在 3.12 版的變更: </span>巨集引數現在僅會被求值一次。如果引數有其他副作用，則不再重複作用。</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="連結到這個定義">¶</a><br /></dt>
<dd><p><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> 巨集的變體，請改用 <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> 而非 <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">在 3.6 版被加入.</span></p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">在 3.12 版的變更: </span>巨集引數現在僅會被求值一次。如果引數有其他副作用，則不再重複作用。</p>
</div>
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以 <a href="https://www.sphinx-doc.org/">Sphinx</a>8.2.3建立。
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