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for example, whether it is <a class="reference internal" href="../glossary.html#term-hashable">hashable</a> or whether it is a <a class="reference internal" href="../glossary.html#term-mapping">mapping</a>. An <a class="reference internal" href="functions.html#issubclass" title="issubclass"><code class="xref py py-func docutils literal notranslate">issubclass()</code></a> or <a class="reference internal" href="functions.html#isinstance" title="isinstance"><code class="xref py py-func docutils literal notranslate">isinstance()</code></a> test for an interface works in one of three ways. 1) A newly written class can inherit directly from one of the abstract base classes. The class must supply the required abstract methods. The remaining mixin methods come from inheritance and can be overridden if desired. Other methods may be added as needed: <div class="highlight-python notranslate"><div class="highlight"><pre>class C(Sequence): # Direct inheritance def __init__(self): ... # Extra method not required by the ABC def __getitem__(self, index): ... # Required abstract method def __len__(self): ... # Required abstract method def count(self, value): ... # Optionally override a mixin method </pre></div> </div> <div class="highlight-pycon notranslate"><div class="highlight"><pre>>>> issubclass(C, Sequence) True >>> isinstance(C(), Sequence) True </pre></div> </div> 2) Existing classes and built-in classes can be registered as “virtual subclasses” of the ABCs. Those classes should define the full API including all of the abstract methods and all of the mixin methods. This lets users rely on <a class="reference internal" href="functions.html#issubclass" title="issubclass"><code class="xref py py-func docutils literal notranslate">issubclass()</code></a> or <a class="reference internal" href="functions.html#isinstance" title="isinstance"><code class="xref py py-func docutils literal notranslate">isinstance()</code></a> tests to determine whether the full interface is supported. The exception to this rule is for methods that are automatically inferred from the rest of the API: <div class="highlight-python notranslate"><div class="highlight"><pre>class D: # No inheritance def __init__(self): ... # Extra method not required by the ABC def __getitem__(self, index): ... # Abstract method def __len__(self): ... # Abstract method def count(self, value): ... # Mixin method def index(self, value): ... # Mixin method Sequence.register(D) # Register instead of inherit </pre></div> </div> <div class="highlight-pycon notranslate"><div class="highlight"><pre>>>> issubclass(D, Sequence) True >>> isinstance(D(), Sequence) True </pre></div> </div> In this example, class <code class="xref py py-class docutils literal notranslate">D</code> does not need to define <code class="docutils literal notranslate">__contains__</code>, <code class="docutils literal notranslate">__iter__</code>, and <code class="docutils literal notranslate">__reversed__</code> because the <a class="reference internal" href="../reference/expressions.html#comparisons">in-operator</a>, the <a class="reference internal" href="../glossary.html#term-iterable">iteration</a> logic, and the <a class="reference internal" href="functions.html#reversed" title="reversed"><code class="xref py py-func docutils literal notranslate">reversed()</code></a> function automatically fall back to using <code class="docutils literal notranslate">__getitem__</code> and <code class="docutils literal notranslate">__len__</code>. 3) Some simple interfaces are directly recognizable by the presence of the required methods (unless those methods have been set to <a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal notranslate">None</code></a>): <div class="highlight-python notranslate"><div class="highlight"><pre>class E: def __iter__(self): ... def __next__(self): ... </pre></div> </div> <div class="highlight-pycon notranslate"><div class="highlight"><pre>>>> issubclass(E, Iterable) True >>> isinstance(E(), Iterable) True </pre></div> </div> Complex interfaces do not support this last technique because an interface is more than just the presence of method names. Interfaces specify semantics and relationships between methods that cannot be inferred solely from the presence of specific method names. For example, knowing that a class supplies <code class="docutils literal notranslate">__getitem__</code>, <code class="docutils literal notranslate">__len__</code>, and <code class="docutils literal notranslate">__iter__</code> is insufficient for distinguishing a <a class="reference internal" href="#collections.abc.Sequence" title="collections.abc.Sequence"><code class="xref py py-class docutils literal notranslate">Sequence</code></a> from a <a class="reference internal" href="#collections.abc.Mapping" title="collections.abc.Mapping"><code class="xref py py-class docutils literal notranslate">Mapping</code></a>. <div class="versionadded"> Added in version 3.9: These abstract classes now support <code class="docutils literal notranslate">[]</code>. See <a class="reference internal" href="stdtypes.html#types-genericalias">Generic Alias Type</a> and <a class="pep reference external" href="https://peps.python.org/pep-0585/">PEP 585</a>. </div> <section id="collections-abstract-base-classes"> <h2>Collections Abstract Base Classes<a class="headerlink" href="#collections-abstract-base-classes" title="Link to this heading">¶</a></h2> The collections module offers the following <a class="reference internal" href="../glossary.html#term-abstract-base-class">ABCs</a>: <table class="docutils align-default"> <thead> <tr class="row-odd"><th class="head">ABC</th> <th class="head">Inherits from</th> <th class="head">Abstract Methods</th> <th class="head">Mixin Methods</th> </tr> </thead> <tbody> <tr class="row-even"><td><a class="reference internal" href="#collections.abc.Container" title="collections.abc.Container"><code class="xref py py-class docutils literal notranslate">Container</code></a> <a class="footnote-reference brackets" href="#id18" id="id2" role="doc-noteref">[1]</a></td> <td></td> <td><code class="docutils literal notranslate">__contains__</code></td> <td></td> </tr> <tr class="row-odd"><td><a class="reference internal" href="#collections.abc.Hashable" title="collections.abc.Hashable"><code class="xref py py-class docutils literal notranslate">Hashable</code></a> <a class="footnote-reference brackets" href="#id18" id="id3" role="doc-noteref">[1]</a></td> <td></td> <td><code class="docutils literal notranslate">__hash__</code></td> <td></td> </tr> <tr class="row-even"><td><a class="reference internal" href="#collections.abc.Iterable" title="collections.abc.Iterable"><code class="xref py py-class docutils literal notranslate">Iterable</code></a> <a class="footnote-reference brackets" href="#id18" id="id4" role="doc-noteref">[1]</a> <a class="footnote-reference brackets" href="#id19" id="id5" role="doc-noteref">[2]</a></td> <td></td> <td><code class="docutils literal notranslate">__iter__</code></td> <td></td> </tr> <tr class="row-odd"><td><a class="reference internal" href="#collections.abc.Iterator" title="collections.abc.Iterator"><code class="xref py py-class docutils literal notranslate">Iterator</code></a> <a class="footnote-reference brackets" href="#id18" id="id6" role="doc-noteref">[1]</a></td> <td><a class="reference internal" href="#collections.abc.Iterable" title="collections.abc.Iterable"><code class="xref py py-class docutils literal notranslate">Iterable</code></a></td> <td><code class="docutils literal notranslate">__next__</code></td> <td><code class="docutils literal notranslate">__iter__</code></td> </tr> <tr class="row-even"><td><a class="reference internal" href="#collections.abc.Reversible" title="collections.abc.Reversible"><code class="xref py py-class docutils literal notranslate">Reversible</code></a> <a class="footnote-reference brackets" href="#id18" id="id7" role="doc-noteref">[1]</a></td> <td><a class="reference internal" href="#collections.abc.Iterable" title="collections.abc.Iterable"><code class="xref py py-class docutils literal notranslate">Iterable</code></a></td> <td><code class="docutils literal notranslate">__reversed__</code></td> <td></td> </tr> <tr class="row-odd"><td><a class="reference internal" href="#collections.abc.Generator" title="collections.abc.Generator"><code class="xref py py-class docutils literal notranslate">Generator</code></a> <a class="footnote-reference brackets" href="#id18" id="id8" role="doc-noteref">[1]</a></td> <td><a class="reference internal" href="#collections.abc.Iterator" title="collections.abc.Iterator"><code class="xref py py-class docutils literal notranslate">Iterator</code></a></td> <td><code class="docutils literal notranslate">send</code>, <code class="docutils literal notranslate">throw</code></td> <td><code class="docutils literal notranslate">close</code>, <code class="docutils literal notranslate">__iter__</code>, <code class="docutils literal notranslate">__next__</code></td> </tr> <tr class="row-even"><td><a class="reference internal" href="#collections.abc.Sized" title="collections.abc.Sized"><code class="xref py py-class docutils literal notranslate">Sized</code></a> <a class="footnote-reference brackets" href="#id18" id="id9" role="doc-noteref">[1]</a></td> <td></td> <td><code class="docutils literal notranslate">__len__</code></td> <td></td> </tr> <tr class="row-odd"><td><a class="reference internal" href="#collections.abc.Callable" title="collections.abc.Callable"><code class="xref py py-class docutils literal notranslate">Callable</code></a> <a class="footnote-reference brackets" href="#id18" id="id10" role="doc-noteref">[1]</a></td> <td></td> <td><code class="docutils literal notranslate">__call__</code></td> <td></td> </tr> <tr class="row-even"><td><a class="reference internal" href="#collections.abc.Collection" title="collections.abc.Collection"><code class="xref py py-class docutils literal notranslate">Collection</code></a> <a class="footnote-reference brackets" href="#id18" id="id11" role="doc-noteref">[1]</a></td> <td><a class="reference internal" href="#collections.abc.Sized" title="collections.abc.Sized"><code class="xref py py-class docutils literal notranslate">Sized</code></a>, <a class="reference internal" href="#collections.abc.Iterable" title="collections.abc.Iterable"><code class="xref py py-class docutils literal notranslate">Iterable</code></a>, <a class="reference internal" href="#collections.abc.Container" title="collections.abc.Container"><code class="xref py py-class docutils literal notranslate">Container</code></a></td> <td><code class="docutils literal notranslate">__contains__</code>, <code class="docutils literal notranslate">__iter__</code>, <code class="docutils literal notranslate">__len__</code></td> <td></td> </tr> <tr class="row-odd"><td><a class="reference internal" href="#collections.abc.Sequence" title="collections.abc.Sequence"><code class="xref py py-class docutils literal notranslate">Sequence</code></a></td> <td><a class="reference internal" href="#collections.abc.Reversible" title="collections.abc.Reversible"><code class="xref py py-class docutils literal notranslate">Reversible</code></a>, <a class="reference internal" href="#collections.abc.Collection" title="collections.abc.Collection"><code class="xref py py-class docutils literal notranslate">Collection</code></a></td> <td><code class="docutils literal notranslate">__getitem__</code>, <code class="docutils literal notranslate">__len__</code></td> <td><code class="docutils literal notranslate">__contains__</code>, <code class="docutils literal notranslate">__iter__</code>, <code class="docutils literal notranslate">__reversed__</code>, <code class="docutils literal notranslate">index</code>, and <code class="docutils literal notranslate">count</code></td> </tr> <tr class="row-even"><td><a class="reference internal" href="#collections.abc.MutableSequence" title="collections.abc.MutableSequence"><code class="xref py py-class docutils literal notranslate">MutableSequence</code></a></td> <td><a class="reference internal" href="#collections.abc.Sequence" title="collections.abc.Sequence"><code class="xref py py-class docutils literal notranslate">Sequence</code></a></td> <td><code class="docutils literal notranslate">__getitem__</code>, <code class="docutils literal notranslate">__setitem__</code>, <code class="docutils literal notranslate">__delitem__</code>, <code class="docutils literal notranslate">__len__</code>, <code class="docutils literal notranslate">insert</code></td> <td>Inherited <a class="reference internal" href="#collections.abc.Sequence" title="collections.abc.Sequence"><code class="xref py py-class docutils literal notranslate">Sequence</code></a> methods and <code class="docutils literal notranslate">append</code>, <code class="docutils literal notranslate">clear</code>, <code class="docutils literal notranslate">reverse</code>, <code class="docutils literal notranslate">extend</code>, <code class="docutils literal notranslate">pop</code>, <code class="docutils literal notranslate">remove</code>, and <code class="docutils literal notranslate">__iadd__</code></td> </tr> <tr class="row-odd"><td><a class="reference internal" href="#collections.abc.ByteString" title="collections.abc.ByteString"><code class="xref py py-class docutils literal notranslate">ByteString</code></a></td> <td><a class="reference internal" href="#collections.abc.Sequence" title="collections.abc.Sequence"><code class="xref py py-class docutils literal notranslate">Sequence</code></a></td> <td><code class="docutils literal notranslate">__getitem__</code>, <code class="docutils literal notranslate">__len__</code></td> <td>Inherited <a class="reference internal" href="#collections.abc.Sequence" title="collections.abc.Sequence"><code class="xref py py-class docutils literal notranslate">Sequence</code></a> methods</td> </tr> <tr class="row-even"><td><a class="reference internal" href="#collections.abc.Set" title="collections.abc.Set"><code class="xref py py-class docutils literal notranslate">Set</code></a></td> <td><a class="reference internal" href="#collections.abc.Collection" title="collections.abc.Collection"><code class="xref py py-class docutils literal notranslate">Collection</code></a></td> <td><code class="docutils literal notranslate">__contains__</code>, <code class="docutils literal notranslate">__iter__</code>, <code class="docutils literal notranslate">__len__</code></td> <td><code class="docutils literal notranslate">__le__</code>, <code class="docutils literal notranslate">__lt__</code>, <code class="docutils literal notranslate">__eq__</code>, <code class="docutils literal notranslate">__ne__</code>, <code class="docutils literal notranslate">__gt__</code>, <code class="docutils literal notranslate">__ge__</code>, <code class="docutils literal notranslate">__and__</code>, <code class="docutils literal notranslate">__or__</code>, <code class="docutils literal notranslate">__sub__</code>, <code class="docutils literal notranslate">__rsub__</code>, <code class="docutils literal notranslate">__xor__</code>, <code class="docutils literal notranslate">__rxor__</code> and <code class="docutils literal notranslate">isdisjoint</code></td> </tr> <tr class="row-odd"><td><a class="reference internal" href="#collections.abc.MutableSet" title="collections.abc.MutableSet"><code class="xref py py-class docutils literal notranslate">MutableSet</code></a></td> <td><a class="reference internal" href="#collections.abc.Set" title="collections.abc.Set"><code class="xref py py-class docutils literal notranslate">Set</code></a></td> <td><code class="docutils literal notranslate">__contains__</code>, <code class="docutils literal notranslate">__iter__</code>, <code class="docutils literal notranslate">__len__</code>, <code class="docutils literal notranslate">add</code>, <code class="docutils literal notranslate">discard</code></td> <td>Inherited <a class="reference internal" href="#collections.abc.Set" title="collections.abc.Set"><code class="xref py py-class docutils literal notranslate">Set</code></a> methods and <code class="docutils literal notranslate">clear</code>, <code class="docutils literal notranslate">pop</code>, <code class="docutils literal notranslate">remove</code>, <code class="docutils literal notranslate">__ior__</code>, <code class="docutils literal notranslate">__iand__</code>, <code class="docutils literal notranslate">__ixor__</code>, and <code class="docutils literal notranslate">__isub__</code></td> </tr> <tr class="row-even"><td><a class="reference internal" href="#collections.abc.Mapping" title="collections.abc.Mapping"><code class="xref py py-class docutils literal notranslate">Mapping</code></a></td> <td><a class="reference internal" href="#collections.abc.Collection" title="collections.abc.Collection"><code class="xref py py-class docutils literal notranslate">Collection</code></a></td> <td><code class="docutils literal notranslate">__getitem__</code>, <code class="docutils literal notranslate">__iter__</code>, <code class="docutils literal notranslate">__len__</code></td> <td><code class="docutils literal notranslate">__contains__</code>, <code class="docutils literal notranslate">keys</code>, <code class="docutils literal notranslate">items</code>, <code class="docutils literal notranslate">values</code>, <code class="docutils literal notranslate">get</code>, <code class="docutils literal notranslate">__eq__</code>, and <code class="docutils literal notranslate">__ne__</code></td> </tr> <tr class="row-odd"><td><a class="reference internal" href="#collections.abc.MutableMapping" title="collections.abc.MutableMapping"><code class="xref py py-class docutils literal notranslate">MutableMapping</code></a></td> <td><a class="reference internal" href="#collections.abc.Mapping" title="collections.abc.Mapping"><code class="xref py py-class docutils literal notranslate">Mapping</code></a></td> <td><code class="docutils literal notranslate">__getitem__</code>, <code class="docutils literal notranslate">__setitem__</code>, <code class="docutils literal notranslate">__delitem__</code>, <code class="docutils literal notranslate">__iter__</code>, <code class="docutils literal notranslate">__len__</code></td> <td>Inherited <a class="reference internal" href="#collections.abc.Mapping" title="collections.abc.Mapping"><code class="xref py py-class docutils literal notranslate">Mapping</code></a> methods and <code class="docutils literal notranslate">pop</code>, <code class="docutils literal notranslate">popitem</code>, <code class="docutils literal notranslate">clear</code>, <code class="docutils literal notranslate">update</code>, and <code class="docutils literal notranslate">setdefault</code></td> </tr> <tr class="row-even"><td><a class="reference internal" href="#collections.abc.MappingView" title="collections.abc.MappingView"><code class="xref py py-class docutils literal notranslate">MappingView</code></a></td> <td><a class="reference internal" href="#collections.abc.Sized" title="collections.abc.Sized"><code class="xref py py-class docutils literal notranslate">Sized</code></a></td> <td></td> <td><code class="docutils literal notranslate">__init__</code>, <code class="docutils literal notranslate">__len__</code> and <code class="docutils literal notranslate">__repr__</code></td> </tr> <tr class="row-odd"><td><a class="reference internal" href="#collections.abc.ItemsView" title="collections.abc.ItemsView"><code class="xref py py-class docutils literal notranslate">ItemsView</code></a></td> <td><a class="reference internal" href="#collections.abc.MappingView" title="collections.abc.MappingView"><code class="xref py py-class docutils literal notranslate">MappingView</code></a>, <a class="reference internal" href="#collections.abc.Set" title="collections.abc.Set"><code class="xref py py-class docutils literal notranslate">Set</code></a></td> <td></td> <td><code class="docutils literal notranslate">__contains__</code>, <code class="docutils literal notranslate">__iter__</code></td> </tr> <tr class="row-even"><td><a class="reference internal" href="#collections.abc.KeysView" title="collections.abc.KeysView"><code class="xref py py-class docutils literal notranslate">KeysView</code></a></td> <td><a class="reference internal" href="#collections.abc.MappingView" title="collections.abc.MappingView"><code class="xref py py-class docutils literal notranslate">MappingView</code></a>, <a class="reference internal" href="#collections.abc.Set" title="collections.abc.Set"><code class="xref py py-class docutils literal notranslate">Set</code></a></td> <td></td> <td><code class="docutils literal notranslate">__contains__</code>, <code class="docutils literal notranslate">__iter__</code></td> </tr> <tr class="row-odd"><td><a class="reference internal" href="#collections.abc.ValuesView" title="collections.abc.ValuesView"><code class="xref py py-class docutils literal notranslate">ValuesView</code></a></td> <td><a class="reference internal" href="#collections.abc.MappingView" title="collections.abc.MappingView"><code class="xref py py-class docutils literal notranslate">MappingView</code></a>, <a class="reference internal" href="#collections.abc.Collection" title="collections.abc.Collection"><code class="xref py py-class docutils literal notranslate">Collection</code></a></td> <td></td> <td><code class="docutils literal notranslate">__contains__</code>, <code class="docutils literal notranslate">__iter__</code></td> </tr> <tr class="row-even"><td><a class="reference internal" href="#collections.abc.Awaitable" title="collections.abc.Awaitable"><code class="xref py py-class docutils literal notranslate">Awaitable</code></a> <a class="footnote-reference brackets" href="#id18" id="id12" role="doc-noteref">[1]</a></td> <td></td> <td><code class="docutils literal notranslate">__await__</code></td> <td></td> </tr> <tr class="row-odd"><td><a class="reference internal" href="#collections.abc.Coroutine" title="collections.abc.Coroutine"><code class="xref py py-class docutils literal notranslate">Coroutine</code></a> <a class="footnote-reference brackets" href="#id18" id="id13" role="doc-noteref">[1]</a></td> <td><a class="reference internal" href="#collections.abc.Awaitable" title="collections.abc.Awaitable"><code class="xref py py-class docutils literal notranslate">Awaitable</code></a></td> <td><code class="docutils literal notranslate">send</code>, <code class="docutils literal notranslate">throw</code></td> <td><code class="docutils literal notranslate">close</code></td> </tr> <tr class="row-even"><td><a class="reference internal" href="#collections.abc.AsyncIterable" title="collections.abc.AsyncIterable"><code class="xref py py-class docutils literal notranslate">AsyncIterable</code></a> <a class="footnote-reference brackets" href="#id18" id="id14" role="doc-noteref">[1]</a></td> <td></td> <td><code class="docutils literal notranslate">__aiter__</code></td> <td></td> </tr> <tr class="row-odd"><td><a class="reference internal" href="#collections.abc.AsyncIterator" title="collections.abc.AsyncIterator"><code class="xref py py-class docutils literal notranslate">AsyncIterator</code></a> <a class="footnote-reference brackets" href="#id18" id="id15" role="doc-noteref">[1]</a></td> <td><a class="reference internal" href="#collections.abc.AsyncIterable" title="collections.abc.AsyncIterable"><code class="xref py py-class docutils literal notranslate">AsyncIterable</code></a></td> <td><code class="docutils literal notranslate">__anext__</code></td> <td><code class="docutils literal notranslate">__aiter__</code></td> </tr> <tr class="row-even"><td><a class="reference internal" href="#collections.abc.AsyncGenerator" title="collections.abc.AsyncGenerator"><code class="xref py py-class docutils literal notranslate">AsyncGenerator</code></a> <a class="footnote-reference brackets" href="#id18" id="id16" role="doc-noteref">[1]</a></td> <td><a class="reference internal" href="#collections.abc.AsyncIterator" title="collections.abc.AsyncIterator"><code class="xref py py-class docutils literal notranslate">AsyncIterator</code></a></td> <td><code class="docutils literal notranslate">asend</code>, <code class="docutils literal notranslate">athrow</code></td> <td><code class="docutils literal notranslate">aclose</code>, <code class="docutils literal notranslate">__aiter__</code>, <code class="docutils literal notranslate">__anext__</code></td> </tr> <tr class="row-odd"><td><a class="reference internal" href="#collections.abc.Buffer" title="collections.abc.Buffer"><code class="xref py py-class docutils literal notranslate">Buffer</code></a> <a class="footnote-reference brackets" href="#id18" id="id17" role="doc-noteref">[1]</a></td> <td></td> <td><code class="docutils literal notranslate">__buffer__</code></td> <td></td> </tr> </tbody> </table> Footnotes <aside class="footnote-list brackets"> <aside class="footnote brackets" id="id18" role="doc-footnote"> [1] (<a role="doc-backlink" href="#id2">1</a>,<a role="doc-backlink" href="#id3">2</a>,<a role="doc-backlink" href="#id4">3</a>,<a role="doc-backlink" href="#id6">4</a>,<a role="doc-backlink" href="#id7">5</a>,<a role="doc-backlink" href="#id8">6</a>,<a role="doc-backlink" href="#id9">7</a>,<a role="doc-backlink" href="#id10">8</a>,<a role="doc-backlink" href="#id11">9</a>,<a role="doc-backlink" href="#id12">10</a>,<a role="doc-backlink" href="#id13">11</a>,<a role="doc-backlink" href="#id14">12</a>,<a role="doc-backlink" href="#id15">13</a>,<a role="doc-backlink" href="#id16">14</a>,<a role="doc-backlink" href="#id17">15</a>) These ABCs override <a class="reference internal" href="abc.html#abc.ABCMeta.__subclasshook__" title="abc.ABCMeta.__subclasshook__"><code class="xref py py-meth docutils literal notranslate">__subclasshook__()</code></a> to support testing an interface by verifying the required methods are present and have not been set to <a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal notranslate">None</code></a>. This only works for simple interfaces. More complex interfaces require registration or direct subclassing. </aside> <aside class="footnote brackets" id="id19" role="doc-footnote"> [<a role="doc-backlink" href="#id5">2</a>] Checking <code class="docutils literal notranslate">isinstance(obj, Iterable)</code> detects classes that are registered as <a class="reference internal" href="#collections.abc.Iterable" title="collections.abc.Iterable"><code class="xref py py-class docutils literal notranslate">Iterable</code></a> or that have an <a class="reference internal" href="stdtypes.html#container.__iter__" title="container.__iter__"><code class="xref py py-meth docutils literal notranslate">__iter__()</code></a> method, but it does not detect classes that iterate with the <a class="reference internal" href="../reference/datamodel.html#object.__getitem__" title="object.__getitem__"><code class="xref py py-meth docutils literal notranslate">__getitem__()</code></a> method. The only reliable way to determine whether an object is <a class="reference internal" href="../glossary.html#term-iterable">iterable</a> is to call <code class="docutils literal notranslate">iter(obj)</code>. </aside> </aside> </section> <section id="collections-abstract-base-classes-detailed-descriptions"> <h2>Collections Abstract Base Classes – Detailed Descriptions<a class="headerlink" href="#collections-abstract-base-classes-detailed-descriptions" title="Link to this heading">¶</a></h2> <dl class="py class"> <dt class="sig sig-object py" id="collections.abc.Container"> class collections.abc.Container<a class="headerlink" href="#collections.abc.Container" title="Link to this definition">¶</a></dt> <dd>ABC for classes that provide the <a class="reference internal" href="../reference/datamodel.html#object.__contains__" title="object.__contains__"><code class="xref py py-meth docutils literal notranslate">__contains__()</code></a> method. </dd></dl> <dl class="py class"> <dt class="sig sig-object py" id="collections.abc.Hashable"> class collections.abc.Hashable<a class="headerlink" href="#collections.abc.Hashable" title="Link to this definition">¶</a></dt> <dd>ABC for classes that provide the <a class="reference internal" href="../reference/datamodel.html#object.__hash__" title="object.__hash__"><code class="xref py py-meth docutils literal notranslate">__hash__()</code></a> method. </dd></dl> <dl class="py class"> <dt class="sig sig-object py" id="collections.abc.Sized"> class collections.abc.Sized<a class="headerlink" href="#collections.abc.Sized" title="Link to this definition">¶</a></dt> <dd>ABC for classes that provide the <a class="reference internal" href="../reference/datamodel.html#object.__len__" title="object.__len__"><code class="xref py py-meth docutils literal notranslate">__len__()</code></a> method. </dd></dl> <dl class="py class"> <dt class="sig sig-object py" id="collections.abc.Callable"> class collections.abc.Callable<a class="headerlink" href="#collections.abc.Callable" title="Link to this definition">¶</a></dt> <dd>ABC for classes that provide the <a class="reference internal" href="../reference/datamodel.html#object.__call__" title="object.__call__"><code class="xref py py-meth docutils literal notranslate">__call__()</code></a> method. See <a class="reference internal" href="typing.html#annotating-callables">Annotating callable objects</a> for details on how to use <code class="xref py py-class docutils literal notranslate">Callable</code> in type annotations. </dd></dl> <dl class="py class"> <dt class="sig sig-object py" id="collections.abc.Iterable"> class collections.abc.Iterable<a class="headerlink" href="#collections.abc.Iterable" title="Link to this definition">¶</a></dt> <dd>ABC for classes that provide the <a class="reference internal" href="stdtypes.html#container.__iter__" title="container.__iter__"><code class="xref py py-meth docutils literal notranslate">__iter__()</code></a> method. Checking <code class="docutils literal notranslate">isinstance(obj, Iterable)</code> detects classes that are registered as <a class="reference internal" href="#collections.abc.Iterable" title="collections.abc.Iterable"><code class="xref py py-class docutils literal notranslate">Iterable</code></a> or that have an <a class="reference internal" href="stdtypes.html#container.__iter__" title="container.__iter__"><code class="xref py py-meth docutils literal notranslate">__iter__()</code></a> method, but it does not detect classes that iterate with the <a class="reference internal" href="../reference/datamodel.html#object.__getitem__" title="object.__getitem__"><code class="xref py py-meth docutils literal notranslate">__getitem__()</code></a> method. The only reliable way to determine whether an object is <a class="reference internal" href="../glossary.html#term-iterable">iterable</a> is to call <code class="docutils literal notranslate">iter(obj)</code>. </dd></dl> <dl class="py class"> <dt class="sig sig-object py" id="collections.abc.Collection"> class collections.abc.Collection<a class="headerlink" href="#collections.abc.Collection" title="Link to this definition">¶</a></dt> <dd>ABC for sized iterable container classes. <div class="versionadded"> Added in version 3.6. </div> </dd></dl> <dl class="py class"> <dt class="sig sig-object py" id="collections.abc.Iterator"> class collections.abc.Iterator<a class="headerlink" href="#collections.abc.Iterator" title="Link to this definition">¶</a></dt> <dd>ABC for classes that provide the <a class="reference internal" href="stdtypes.html#iterator.__iter__" title="iterator.__iter__"><code class="xref py py-meth docutils literal notranslate">__iter__()</code></a> and <a class="reference internal" href="stdtypes.html#iterator.__next__" title="iterator.__next__"><code class="xref py py-meth docutils literal notranslate">__next__()</code></a> methods. See also the definition of <a class="reference internal" href="../glossary.html#term-iterator">iterator</a>. </dd></dl> <dl class="py class"> <dt class="sig sig-object py" id="collections.abc.Reversible"> class collections.abc.Reversible<a class="headerlink" href="#collections.abc.Reversible" title="Link to this definition">¶</a></dt> <dd>ABC for iterable classes that also provide the <a class="reference internal" href="../reference/datamodel.html#object.__reversed__" title="object.__reversed__"><code class="xref py py-meth docutils literal notranslate">__reversed__()</code></a> method. <div class="versionadded"> Added in version 3.6. </div> </dd></dl> <dl class="py class"> <dt class="sig sig-object py" id="collections.abc.Generator"> class collections.abc.Generator<a class="headerlink" href="#collections.abc.Generator" title="Link to this definition">¶</a></dt> <dd>ABC for <a class="reference internal" href="../glossary.html#term-generator">generator</a> classes that implement the protocol defined in <a class="pep reference external" href="https://peps.python.org/pep-0342/">PEP 342</a> that extends <a class="reference internal" href="../glossary.html#term-iterator">iterators</a> with the <a class="reference internal" href="../reference/expressions.html#generator.send" title="generator.send"><code class="xref py py-meth docutils literal notranslate">send()</code></a>, <a class="reference internal" href="../reference/expressions.html#generator.throw" title="generator.throw"><code class="xref py py-meth docutils literal notranslate">throw()</code></a> and <a class="reference internal" href="../reference/expressions.html#generator.close" title="generator.close"><code class="xref py py-meth docutils literal notranslate">close()</code></a> methods. See <a class="reference internal" href="typing.html#annotating-generators-and-coroutines">Annotating generators and coroutines</a> for details on using <code class="xref py py-class docutils literal notranslate">Generator</code> in type annotations. <div class="versionadded"> Added in version 3.5. </div> </dd></dl> <dl class="py class"> <dt class="sig sig-object py" id="collections.abc.Sequence"> class collections.abc.Sequence<a class="headerlink" href="#collections.abc.Sequence" title="Link to this definition">¶</a></dt> <dt class="sig sig-object py" id="collections.abc.MutableSequence"> class collections.abc.MutableSequence<a class="headerlink" href="#collections.abc.MutableSequence" title="Link to this definition">¶</a></dt> <dt class="sig sig-object py" id="collections.abc.ByteString"> class collections.abc.ByteString<a class="headerlink" href="#collections.abc.ByteString" title="Link to this definition">¶</a></dt> <dd>ABCs for read-only and mutable <a class="reference internal" href="../glossary.html#term-sequence">sequences</a>. Implementation note: Some of the mixin methods, such as <a class="reference internal" href="stdtypes.html#container.__iter__" title="container.__iter__"><code class="xref py py-meth docutils literal notranslate">__iter__()</code></a>, <a class="reference internal" href="../reference/datamodel.html#object.__reversed__" title="object.__reversed__"><code class="xref py py-meth docutils literal notranslate">__reversed__()</code></a> and <code class="xref py py-meth docutils literal notranslate">index()</code>, make repeated calls to the underlying <a class="reference internal" href="../reference/datamodel.html#object.__getitem__" title="object.__getitem__"><code class="xref py py-meth docutils literal notranslate">__getitem__()</code></a> method. Consequently, if <a class="reference internal" href="../reference/datamodel.html#object.__getitem__" title="object.__getitem__"><code class="xref py py-meth docutils literal notranslate">__getitem__()</code></a> is implemented with constant access speed, the mixin methods will have linear performance; however, if the underlying method is linear (as it would be with a linked list), the mixins will have quadratic performance and will likely need to be overridden. <div class="versionchanged"> Changed in version 3.5: The index() method added support for stop and start arguments. </div> <div class="deprecated-removed"> Deprecated since version 3.12, will be removed in version 3.14: The <a class="reference internal" href="#collections.abc.ByteString" title="collections.abc.ByteString"><code class="xref py py-class docutils literal notranslate">ByteString</code></a> ABC has been deprecated. For use in typing, prefer a union, like <code class="docutils literal notranslate">bytes | bytearray</code>, or <a class="reference internal" href="#collections.abc.Buffer" title="collections.abc.Buffer"><code class="xref py py-class docutils literal notranslate">collections.abc.Buffer</code></a>. For use as an ABC, prefer <a class="reference internal" href="#collections.abc.Sequence" title="collections.abc.Sequence"><code class="xref py py-class docutils literal notranslate">Sequence</code></a> or <a class="reference internal" href="#collections.abc.Buffer" title="collections.abc.Buffer"><code class="xref py py-class docutils literal notranslate">collections.abc.Buffer</code></a>. </div> </dd></dl> <dl class="py class"> <dt class="sig sig-object py" id="collections.abc.Set"> class collections.abc.Set<a class="headerlink" href="#collections.abc.Set" title="Link to this definition">¶</a></dt> <dt class="sig sig-object py" id="collections.abc.MutableSet"> class collections.abc.MutableSet<a class="headerlink" href="#collections.abc.MutableSet" title="Link to this definition">¶</a></dt> <dd>ABCs for read-only and mutable <a class="reference internal" href="stdtypes.html#types-set">sets</a>. </dd></dl> <dl class="py class"> <dt class="sig sig-object py" id="collections.abc.Mapping"> class collections.abc.Mapping<a class="headerlink" href="#collections.abc.Mapping" title="Link to this definition">¶</a></dt> <dt class="sig sig-object py" id="collections.abc.MutableMapping"> class collections.abc.MutableMapping<a class="headerlink" href="#collections.abc.MutableMapping" title="Link to this definition">¶</a></dt> <dd>ABCs for read-only and mutable <a class="reference internal" href="../glossary.html#term-mapping">mappings</a>. </dd></dl> <dl class="py class"> <dt class="sig sig-object py" id="collections.abc.MappingView"> class collections.abc.MappingView<a class="headerlink" href="#collections.abc.MappingView" title="Link to this definition">¶</a></dt> <dt class="sig sig-object py" id="collections.abc.ItemsView"> class collections.abc.ItemsView<a class="headerlink" href="#collections.abc.ItemsView" title="Link to this definition">¶</a></dt> <dt class="sig sig-object py" id="collections.abc.KeysView"> class collections.abc.KeysView<a class="headerlink" href="#collections.abc.KeysView" title="Link to this definition">¶</a></dt> <dt class="sig sig-object py" id="collections.abc.ValuesView"> class collections.abc.ValuesView<a class="headerlink" href="#collections.abc.ValuesView" title="Link to this definition">¶</a></dt> <dd>ABCs for mapping, items, keys, and values <a class="reference internal" href="../glossary.html#term-dictionary-view">views</a>. </dd></dl> <dl class="py class"> <dt class="sig sig-object py" id="collections.abc.Awaitable"> class collections.abc.Awaitable<a class="headerlink" href="#collections.abc.Awaitable" title="Link to this definition">¶</a></dt> <dd>ABC for <a class="reference internal" href="../glossary.html#term-awaitable">awaitable</a> objects, which can be used in <a class="reference internal" href="../reference/expressions.html#await"><code class="xref std std-keyword docutils literal notranslate">await</code></a> expressions. Custom implementations must provide the <a class="reference internal" href="../reference/datamodel.html#object.__await__" title="object.__await__"><code class="xref py py-meth docutils literal notranslate">__await__()</code></a> method. <a class="reference internal" href="../glossary.html#term-coroutine">Coroutine</a> objects and instances of the <a class="reference internal" href="#collections.abc.Coroutine" title="collections.abc.Coroutine"><code class="xref py py-class docutils literal notranslate">Coroutine</code></a> ABC are all instances of this ABC. <div class="admonition note"> Note In CPython, generator-based coroutines (<a class="reference internal" href="../glossary.html#term-generator">generators</a> decorated with <a class="reference internal" href="types.html#types.coroutine" title="types.coroutine"><code class="xref py py-func docutils literal notranslate">@types.coroutine</code></a>) are awaitables, even though they do not have an <a class="reference internal" href="../reference/datamodel.html#object.__await__" title="object.__await__"><code class="xref py py-meth docutils literal notranslate">__await__()</code></a> method. Using <code class="docutils literal notranslate">isinstance(gencoro, Awaitable)</code> for them will return <code class="docutils literal notranslate">False</code>. Use <a class="reference internal" href="inspect.html#inspect.isawaitable" title="inspect.isawaitable"><code class="xref py py-func docutils literal notranslate">inspect.isawaitable()</code></a> to detect them. </div> <div class="versionadded"> Added in version 3.5. </div> </dd></dl> <dl class="py class"> <dt class="sig sig-object py" id="collections.abc.Coroutine"> class collections.abc.Coroutine<a class="headerlink" href="#collections.abc.Coroutine" title="Link to this definition">¶</a></dt> <dd>ABC for <a class="reference internal" href="../glossary.html#term-coroutine">coroutine</a> compatible classes. These implement the following methods, defined in <a class="reference internal" href="../reference/datamodel.html#coroutine-objects">Coroutine Objects</a>: <a class="reference internal" href="../reference/datamodel.html#coroutine.send" title="coroutine.send"><code class="xref py py-meth docutils literal notranslate">send()</code></a>, <a class="reference internal" href="../reference/datamodel.html#coroutine.throw" title="coroutine.throw"><code class="xref py py-meth docutils literal notranslate">throw()</code></a>, and <a class="reference internal" href="../reference/datamodel.html#coroutine.close" title="coroutine.close"><code class="xref py py-meth docutils literal notranslate">close()</code></a>. Custom implementations must also implement <a class="reference internal" href="../reference/datamodel.html#object.__await__" title="object.__await__"><code class="xref py py-meth docutils literal notranslate">__await__()</code></a>. All <a class="reference internal" href="#collections.abc.Coroutine" title="collections.abc.Coroutine"><code class="xref py py-class docutils literal notranslate">Coroutine</code></a> instances are also instances of <a class="reference internal" href="#collections.abc.Awaitable" title="collections.abc.Awaitable"><code class="xref py py-class docutils literal notranslate">Awaitable</code></a>. <div class="admonition note"> Note In CPython, generator-based coroutines (<a class="reference internal" href="../glossary.html#term-generator">generators</a> decorated with <a class="reference internal" href="types.html#types.coroutine" title="types.coroutine"><code class="xref py py-func docutils literal notranslate">@types.coroutine</code></a>) are awaitables, even though they do not have an <a class="reference internal" href="../reference/datamodel.html#object.__await__" title="object.__await__"><code class="xref py py-meth docutils literal notranslate">__await__()</code></a> method. Using <code class="docutils literal notranslate">isinstance(gencoro, Coroutine)</code> for them will return <code class="docutils literal notranslate">False</code>. Use <a class="reference internal" href="inspect.html#inspect.isawaitable" title="inspect.isawaitable"><code class="xref py py-func docutils literal notranslate">inspect.isawaitable()</code></a> to detect them. </div> See <a class="reference internal" href="typing.html#annotating-generators-and-coroutines">Annotating generators and coroutines</a> for details on using <code class="xref py py-class docutils literal notranslate">Coroutine</code> in type annotations. The variance and order of type parameters correspond to those of <a class="reference internal" href="#collections.abc.Generator" title="collections.abc.Generator"><code class="xref py py-class docutils literal notranslate">Generator</code></a>. <div class="versionadded"> Added in version 3.5. </div> </dd></dl> <dl class="py class"> <dt class="sig sig-object py" id="collections.abc.AsyncIterable"> class collections.abc.AsyncIterable<a class="headerlink" href="#collections.abc.AsyncIterable" title="Link to this definition">¶</a></dt> <dd>ABC for classes that provide an <code class="docutils literal notranslate">__aiter__</code> method. See also the definition of <a class="reference internal" href="../glossary.html#term-asynchronous-iterable">asynchronous iterable</a>. <div class="versionadded"> Added in version 3.5. </div> </dd></dl> <dl class="py class"> <dt class="sig sig-object py" id="collections.abc.AsyncIterator"> class collections.abc.AsyncIterator<a class="headerlink" href="#collections.abc.AsyncIterator" title="Link to this definition">¶</a></dt> <dd>ABC for classes that provide <code class="docutils literal notranslate">__aiter__</code> and <code class="docutils literal notranslate">__anext__</code> methods. See also the definition of <a class="reference internal" href="../glossary.html#term-asynchronous-iterator">asynchronous iterator</a>. <div class="versionadded"> Added in version 3.5. </div> </dd></dl> <dl class="py class"> <dt class="sig sig-object py" id="collections.abc.AsyncGenerator"> class collections.abc.AsyncGenerator<a class="headerlink" href="#collections.abc.AsyncGenerator" title="Link to this definition">¶</a></dt> <dd>ABC for <a class="reference internal" href="../glossary.html#term-asynchronous-generator">asynchronous generator</a> classes that implement the protocol defined in <a class="pep reference external" href="https://peps.python.org/pep-0525/">PEP 525</a> and <a class="pep reference external" href="https://peps.python.org/pep-0492/">PEP 492</a>. See <a class="reference internal" href="typing.html#annotating-generators-and-coroutines">Annotating generators and coroutines</a> for details on using <code class="xref py py-class docutils literal notranslate">AsyncGenerator</code> in type annotations. <div class="versionadded"> Added in version 3.6. </div> </dd></dl> <dl class="py class"> <dt class="sig sig-object py" id="collections.abc.Buffer"> class collections.abc.Buffer<a class="headerlink" href="#collections.abc.Buffer" title="Link to this definition">¶</a></dt> <dd>ABC for classes that provide the <a class="reference internal" href="../reference/datamodel.html#object.__buffer__" title="object.__buffer__"><code class="xref py py-meth docutils literal notranslate">__buffer__()</code></a> method, implementing the <a class="reference internal" href="../c-api/buffer.html#bufferobjects">buffer protocol</a>. See <a class="pep reference external" href="https://peps.python.org/pep-0688/">PEP 688</a>. <div class="versionadded"> Added in version 3.12. </div> </dd></dl> </section> <section id="examples-and-recipes"> <h2>Examples and Recipes<a class="headerlink" href="#examples-and-recipes" title="Link to this heading">¶</a></h2> ABCs allow us to ask classes or instances if they provide particular functionality, for example: <div class="highlight-python3 notranslate"><div class="highlight"><pre>size = None if isinstance(myvar, collections.abc.Sized): size = len(myvar) </pre></div> </div> Several of the ABCs are also useful as mixins that make it easier to develop classes supporting container APIs. For example, to write a class supporting the full <a class="reference internal" href="#collections.abc.Set" title="collections.abc.Set"><code class="xref py py-class docutils literal notranslate">Set</code></a> API, it is only necessary to supply the three underlying abstract methods: <a class="reference internal" href="../reference/datamodel.html#object.__contains__" title="object.__contains__"><code class="xref py py-meth docutils literal notranslate">__contains__()</code></a>, <a class="reference internal" href="stdtypes.html#container.__iter__" title="container.__iter__"><code class="xref py py-meth docutils literal notranslate">__iter__()</code></a>, and <a class="reference internal" href="../reference/datamodel.html#object.__len__" title="object.__len__"><code class="xref py py-meth docutils literal notranslate">__len__()</code></a>. The ABC supplies the remaining methods such as <code class="xref py py-meth docutils literal notranslate">__and__()</code> and <a class="reference internal" href="stdtypes.html#frozenset.isdisjoint" title="frozenset.isdisjoint"><code class="xref py py-meth docutils literal notranslate">isdisjoint()</code></a>: <div class="highlight-python3 notranslate"><div class="highlight"><pre>class ListBasedSet(collections.abc.Set): ''' Alternate set implementation favoring space over speed and not requiring the set elements to be hashable. ''' def __init__(self, iterable): self.elements = lst = [] for value in iterable: if value not in lst: lst.append(value) def __iter__(self): return iter(self.elements) def __contains__(self, value): return value in self.elements def __len__(self): return len(self.elements) s1 = ListBasedSet('abcdef') s2 = ListBasedSet('defghi') overlap = s1 & s2 # The __and__() method is supported automatically </pre></div> </div> Notes on using <a class="reference internal" href="#collections.abc.Set" title="collections.abc.Set"><code class="xref py py-class docutils literal notranslate">Set</code></a> and <a class="reference internal" href="#collections.abc.MutableSet" title="collections.abc.MutableSet"><code class="xref py py-class docutils literal notranslate">MutableSet</code></a> as a mixin: <ol class="arabic simple"> <li>Since some set operations create new sets, the default mixin methods need a way to create new instances from an <a class="reference internal" href="../glossary.html#term-iterable">iterable</a>. The class constructor is assumed to have a signature in the form <code class="docutils literal notranslate">ClassName(iterable)</code>. That assumption is factored-out to an internal <a class="reference internal" href="functions.html#classmethod" title="classmethod"><code class="xref py py-class docutils literal notranslate">classmethod</code></a> called <code class="xref py py-meth docutils literal notranslate">_from_iterable()</code> which calls <code class="docutils literal notranslate">cls(iterable)</code> to produce a new set. If the <a class="reference internal" href="#collections.abc.Set" title="collections.abc.Set"><code class="xref py py-class docutils literal notranslate">Set</code></a> mixin is being used in a class with a different constructor signature, you will need to override <code class="xref py py-meth docutils literal notranslate">_from_iterable()</code> with a classmethod or regular method that can construct new instances from an iterable argument.</li> <li>To override the comparisons (presumably for speed, as the semantics are fixed), redefine <a class="reference internal" href="../reference/datamodel.html#object.__le__" title="object.__le__"><code class="xref py py-meth docutils literal notranslate">__le__()</code></a> and <a class="reference internal" href="../reference/datamodel.html#object.__ge__" title="object.__ge__"><code class="xref py py-meth docutils literal notranslate">__ge__()</code></a>, then the other operations will automatically follow suit.</li> <li>The <a class="reference internal" href="#collections.abc.Set" title="collections.abc.Set"><code class="xref py py-class docutils literal notranslate">Set</code></a> mixin provides a <code class="xref py py-meth docutils literal notranslate">_hash()</code> method to compute a hash value for the set; however, <a class="reference internal" href="../reference/datamodel.html#object.__hash__" title="object.__hash__"><code class="xref py py-meth docutils literal notranslate">__hash__()</code></a> is not defined because not all sets are <a class="reference internal" href="../glossary.html#term-hashable">hashable</a> or immutable. To add set hashability using mixins, inherit from both <a class="reference internal" href="#collections.abc.Set" title="collections.abc.Set"><code class="xref py py-meth docutils literal notranslate">Set()</code></a> and <a class="reference internal" href="#collections.abc.Hashable" title="collections.abc.Hashable"><code class="xref py py-meth docutils literal notranslate">Hashable()</code></a>, then define <code class="docutils literal notranslate">__hash__ = Set._hash</code>.</li> </ol> <div class="admonition seealso"> See also <ul class="simple"> <li><a class="reference external" href="https://code.activestate.com/recipes/576694/">OrderedSet recipe</a> for an example built on <a class="reference internal" href="#collections.abc.MutableSet" title="collections.abc.MutableSet"><code class="xref py py-class docutils literal notranslate">MutableSet</code></a>.</li> <li>For more about ABCs, see the <a class="reference internal" href="abc.html#module-abc" title="abc: Abstract base classes according to :pep:`3119`."><code class="xref py py-mod docutils literal notranslate">abc</code></a> module and <a class="pep reference external" href="https://peps.python.org/pep-3119/">PEP 3119</a>.</li> </ul> </div> </section> </section> <div class="clearer"></div> </div> </div> </div> <div class="sphinxsidebar" role="navigation" aria-label="Main"> <div class="sphinxsidebarwrapper"> <div> <h3><a href="../contents.html">Table of Contents</a></h3> <ul> <li><a class="reference internal" href="#"><code class="xref py py-mod docutils literal notranslate">collections.abc</code> — Abstract Base Classes for Containers</a><ul> <li><a class="reference internal" href="#collections-abstract-base-classes">Collections Abstract Base Classes</a></li> <li><a class="reference internal" href="#collections-abstract-base-classes-detailed-descriptions">Collections Abstract Base Classes – Detailed Descriptions</a></li> <li><a class="reference internal" href="#examples-and-recipes">Examples and Recipes</a></li> </ul> </li> </ul> </div> <div> <h4>Previous topic</h4> <a href="collections.html" title="previous chapter"><code class="xref py py-mod docutils literal notranslate">collections</code> — Container datatypes</a> </div> <div> <h4>Next topic</h4> <a href="heapq.html" title="next chapter"><code class="xref py py-mod docutils literal notranslate">heapq</code> — Heap queue algorithm</a> </div> <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/main/Doc/library/collections.abc.rst" rel="nofollow">Show Source </a> </li> </ul> </div> </div> <div id="sidebarbutton" title="Collapse sidebar"> « </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="heapq.html" title="heapq — Heap queue algorithm" >next</a> |</li> <li class="right" > <a href="collections.html" title="collections — Container datatypes" >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">3.13.2 Documentation</a> » </li> <li class="nav-item nav-item-1"><a href="index.html" >The Python Standard Library</a> »</li> <li class="nav-item nav-item-2"><a href="datatypes.html" >Data Types</a> »</li> <li class="nav-item nav-item-this"><a href=""><code class="xref py py-mod docutils literal notranslate">collections.abc</code> — Abstract Base Classes for Containers</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"> © <a href="../copyright.html"> Copyright </a> 2001-2025, Python Software Foundation. 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