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<li><a class="reference internal" href="#"><code class="xref py py-mod docutils literal notranslate"><span class="pre">__future__</span></code> — Future statement definitions</a><ul>
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  <section id="module-__future__">
<span id="future-future-statement-definitions"></span><h1><code class="xref py py-mod docutils literal notranslate"><span class="pre">__future__</span></code> — Future statement definitions<a class="headerlink" href="#module-__future__" title="Link to this heading">¶</a></h1>
<p><strong>Source code:</strong> <a class="extlink-source reference external" href="https://github.com/python/cpython/tree/main/Lib/__future__.py">Lib/__future__.py</a></p>
<hr class="docutils" />
<p>Imports of the form <code class="docutils literal notranslate"><span class="pre">from</span> <span class="pre">__future__</span> <span class="pre">import</span> <span class="pre">feature</span></code> are called
<a class="reference internal" href="../reference/simple_stmts.html#future"><span class="std std-ref">future statements</span></a>. These are special-cased by the Python compiler
to allow the use of new Python features in modules containing the future statement
before the release in which the feature becomes standard.</p>
<p>While these future statements are given additional special meaning by the
Python compiler, they are still executed like any other import statement and
the <code class="xref py py-mod docutils literal notranslate"><span class="pre">__future__</span></code> exists and is handled by the import system the same way
any other Python module would be. This design serves three purposes:</p>
<ul class="simple">
<li><p>To avoid confusing existing tools that analyze import statements and expect to
find the modules they’re importing.</p></li>
<li><p>To document when incompatible changes were introduced, and when they will be
— or were — made mandatory.  This is a form of executable documentation, and
can be inspected programmatically via importing <code class="xref py py-mod docutils literal notranslate"><span class="pre">__future__</span></code> and examining
its contents.</p></li>
<li><p>To ensure that <a class="reference internal" href="../reference/simple_stmts.html#future"><span class="std std-ref">future statements</span></a> run under releases prior to
Python 2.1 at least yield runtime exceptions (the import of <code class="xref py py-mod docutils literal notranslate"><span class="pre">__future__</span></code>
will fail, because there was no module of that name prior to 2.1).</p></li>
</ul>
<section id="module-contents">
<h2>Module Contents<a class="headerlink" href="#module-contents" title="Link to this heading">¶</a></h2>
<p>No feature description will ever be deleted from <code class="xref py py-mod docutils literal notranslate"><span class="pre">__future__</span></code>. Since its
introduction in Python 2.1 the following features have found their way into the
language using this mechanism:</p>
<table class="docutils align-default">
<thead>
<tr class="row-odd"><th class="head"><p>feature</p></th>
<th class="head"><p>optional in</p></th>
<th class="head"><p>mandatory in</p></th>
<th class="head"><p>effect</p></th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><dl class="py data">
<dt class="sig sig-object py" id="future__.nested_scopes">
<span class="sig-prename descclassname"><span class="pre">__future__.</span></span><span class="sig-name descname"><span class="pre">nested_scopes</span></span><a class="headerlink" href="#future__.nested_scopes" title="Link to this definition">¶</a></dt>
<dd></dd></dl>

</td>
<td><p>2.1.0b1</p></td>
<td><p>2.2</p></td>
<td><p><span class="target" id="index-0"></span><a class="pep reference external" href="https://peps.python.org/pep-0227/"><strong>PEP 227</strong></a>: <em>Statically Nested Scopes</em></p></td>
</tr>
<tr class="row-odd"><td><dl class="py data">
<dt class="sig sig-object py" id="future__.generators">
<span class="sig-prename descclassname"><span class="pre">__future__.</span></span><span class="sig-name descname"><span class="pre">generators</span></span><a class="headerlink" href="#future__.generators" title="Link to this definition">¶</a></dt>
<dd></dd></dl>

</td>
<td><p>2.2.0a1</p></td>
<td><p>2.3</p></td>
<td><p><span class="target" id="index-1"></span><a class="pep reference external" href="https://peps.python.org/pep-0255/"><strong>PEP 255</strong></a>: <em>Simple Generators</em></p></td>
</tr>
<tr class="row-even"><td><dl class="py data">
<dt class="sig sig-object py" id="future__.division">
<span class="sig-prename descclassname"><span class="pre">__future__.</span></span><span class="sig-name descname"><span class="pre">division</span></span><a class="headerlink" href="#future__.division" title="Link to this definition">¶</a></dt>
<dd></dd></dl>

</td>
<td><p>2.2.0a2</p></td>
<td><p>3.0</p></td>
<td><p><span class="target" id="index-2"></span><a class="pep reference external" href="https://peps.python.org/pep-0238/"><strong>PEP 238</strong></a>: <em>Changing the Division Operator</em></p></td>
</tr>
<tr class="row-odd"><td><dl class="py data">
<dt class="sig sig-object py" id="future__.absolute_import">
<span class="sig-prename descclassname"><span class="pre">__future__.</span></span><span class="sig-name descname"><span class="pre">absolute_import</span></span><a class="headerlink" href="#future__.absolute_import" title="Link to this definition">¶</a></dt>
<dd></dd></dl>

</td>
<td><p>2.5.0a1</p></td>
<td><p>3.0</p></td>
<td><p><span class="target" id="index-3"></span><a class="pep reference external" href="https://peps.python.org/pep-0328/"><strong>PEP 328</strong></a>: <em>Imports: Multi-Line and Absolute/Relative</em></p></td>
</tr>
<tr class="row-even"><td><dl class="py data">
<dt class="sig sig-object py" id="future__.with_statement">
<span class="sig-prename descclassname"><span class="pre">__future__.</span></span><span class="sig-name descname"><span class="pre">with_statement</span></span><a class="headerlink" href="#future__.with_statement" title="Link to this definition">¶</a></dt>
<dd></dd></dl>

</td>
<td><p>2.5.0a1</p></td>
<td><p>2.6</p></td>
<td><p><span class="target" id="index-4"></span><a class="pep reference external" href="https://peps.python.org/pep-0343/"><strong>PEP 343</strong></a>: <em>The “with” Statement</em></p></td>
</tr>
<tr class="row-odd"><td><dl class="py data">
<dt class="sig sig-object py" id="future__.print_function">
<span class="sig-prename descclassname"><span class="pre">__future__.</span></span><span class="sig-name descname"><span class="pre">print_function</span></span><a class="headerlink" href="#future__.print_function" title="Link to this definition">¶</a></dt>
<dd></dd></dl>

</td>
<td><p>2.6.0a2</p></td>
<td><p>3.0</p></td>
<td><p><span class="target" id="index-5"></span><a class="pep reference external" href="https://peps.python.org/pep-3105/"><strong>PEP 3105</strong></a>: <em>Make print a function</em></p></td>
</tr>
<tr class="row-even"><td><dl class="py data">
<dt class="sig sig-object py" id="future__.unicode_literals">
<span class="sig-prename descclassname"><span class="pre">__future__.</span></span><span class="sig-name descname"><span class="pre">unicode_literals</span></span><a class="headerlink" href="#future__.unicode_literals" title="Link to this definition">¶</a></dt>
<dd></dd></dl>

</td>
<td><p>2.6.0a2</p></td>
<td><p>3.0</p></td>
<td><p><span class="target" id="index-6"></span><a class="pep reference external" href="https://peps.python.org/pep-3112/"><strong>PEP 3112</strong></a>: <em>Bytes literals in Python 3000</em></p></td>
</tr>
<tr class="row-odd"><td><dl class="py data">
<dt class="sig sig-object py" id="future__.generator_stop">
<span class="sig-prename descclassname"><span class="pre">__future__.</span></span><span class="sig-name descname"><span class="pre">generator_stop</span></span><a class="headerlink" href="#future__.generator_stop" title="Link to this definition">¶</a></dt>
<dd></dd></dl>

</td>
<td><p>3.5.0b1</p></td>
<td><p>3.7</p></td>
<td><p><span class="target" id="index-7"></span><a class="pep reference external" href="https://peps.python.org/pep-0479/"><strong>PEP 479</strong></a>: <em>StopIteration handling inside generators</em></p></td>
</tr>
<tr class="row-even"><td><dl class="py data">
<dt class="sig sig-object py" id="future__.annotations">
<span class="sig-prename descclassname"><span class="pre">__future__.</span></span><span class="sig-name descname"><span class="pre">annotations</span></span><a class="headerlink" href="#future__.annotations" title="Link to this definition">¶</a></dt>
<dd></dd></dl>

</td>
<td><p>3.7.0b1</p></td>
<td><p>Never <a class="footnote-reference brackets" href="#id2" id="id1" role="doc-noteref"><span class="fn-bracket">[</span>1<span class="fn-bracket">]</span></a></p></td>
<td><p><span class="target" id="index-8"></span><a class="pep reference external" href="https://peps.python.org/pep-0563/"><strong>PEP 563</strong></a>: <em>Postponed evaluation of annotations</em>,
<span class="target" id="index-9"></span><a class="pep reference external" href="https://peps.python.org/pep-0649/"><strong>PEP 649</strong></a>: <em>Deferred evaluation of annotations using descriptors</em></p></td>
</tr>
</tbody>
</table>
<dl class="py class" id="future-classes">
<dt class="sig sig-object py" id="future__._Feature">
<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">__future__.</span></span><span class="sig-name descname"><span class="pre">_Feature</span></span><a class="headerlink" href="#future__._Feature" title="Link to this definition">¶</a></dt>
<dd><p>Each statement in <code class="file docutils literal notranslate"><span class="pre">__future__.py</span></code> is of the form:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">FeatureName</span> <span class="o">=</span> <span class="n">_Feature</span><span class="p">(</span><span class="n">OptionalRelease</span><span class="p">,</span> <span class="n">MandatoryRelease</span><span class="p">,</span>
                       <span class="n">CompilerFlag</span><span class="p">)</span>
</pre></div>
</div>
<p>where, normally, <em>OptionalRelease</em> is less than <em>MandatoryRelease</em>, and both are
5-tuples of the same form as <a class="reference internal" href="sys.html#sys.version_info" title="sys.version_info"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.version_info</span></code></a>:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="p">(</span><span class="n">PY_MAJOR_VERSION</span><span class="p">,</span> <span class="c1"># the 2 in 2.1.0a3; an int</span>
 <span class="n">PY_MINOR_VERSION</span><span class="p">,</span> <span class="c1"># the 1; an int</span>
 <span class="n">PY_MICRO_VERSION</span><span class="p">,</span> <span class="c1"># the 0; an int</span>
 <span class="n">PY_RELEASE_LEVEL</span><span class="p">,</span> <span class="c1"># &quot;alpha&quot;, &quot;beta&quot;, &quot;candidate&quot; or &quot;final&quot;; string</span>
 <span class="n">PY_RELEASE_SERIAL</span> <span class="c1"># the 3; an int</span>
<span class="p">)</span>
</pre></div>
</div>
</dd></dl>

<dl class="py method">
<dt class="sig sig-object py" id="future__._Feature.getOptionalRelease">
<span class="sig-prename descclassname"><span class="pre">_Feature.</span></span><span class="sig-name descname"><span class="pre">getOptionalRelease</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#future__._Feature.getOptionalRelease" title="Link to this definition">¶</a></dt>
<dd><p><em>OptionalRelease</em> records the first release in which the feature was accepted.</p>
</dd></dl>

<dl class="py method">
<dt class="sig sig-object py" id="future__._Feature.getMandatoryRelease">
<span class="sig-prename descclassname"><span class="pre">_Feature.</span></span><span class="sig-name descname"><span class="pre">getMandatoryRelease</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#future__._Feature.getMandatoryRelease" title="Link to this definition">¶</a></dt>
<dd><p>In the case of a <em>MandatoryRelease</em> that has not yet occurred,
<em>MandatoryRelease</em> predicts the release in which the feature will become part of
the language.</p>
<p>Else <em>MandatoryRelease</em> records when the feature became part of the language; in
releases at or after that, modules no longer need a future statement to use the
feature in question, but may continue to use such imports.</p>
<p><em>MandatoryRelease</em> may also be <code class="docutils literal notranslate"><span class="pre">None</span></code>, meaning that a planned feature got
dropped or that it is not yet decided.</p>
</dd></dl>

<dl class="py attribute">
<dt class="sig sig-object py" id="future__._Feature.compiler_flag">
<span class="sig-prename descclassname"><span class="pre">_Feature.</span></span><span class="sig-name descname"><span class="pre">compiler_flag</span></span><a class="headerlink" href="#future__._Feature.compiler_flag" title="Link to this definition">¶</a></dt>
<dd><p><em>CompilerFlag</em> is the (bitfield) flag that should be passed in the fourth
argument to the built-in function <a class="reference internal" href="functions.html#compile" title="compile"><code class="xref py py-func docutils literal notranslate"><span class="pre">compile()</span></code></a> to enable the feature in
dynamically compiled code.  This flag is stored in the <code class="xref py py-attr docutils literal notranslate"><span class="pre">_Feature.compiler_flag</span></code>
attribute on <a class="reference internal" href="#future__._Feature" title="__future__._Feature"><code class="xref py py-class docutils literal notranslate"><span class="pre">_Feature</span></code></a> instances.</p>
</dd></dl>

<aside class="footnote-list brackets">
<aside class="footnote brackets" id="id2" role="doc-footnote">
<span class="label"><span class="fn-bracket">[</span><a role="doc-backlink" href="#id1">1</a><span class="fn-bracket">]</span></span>
<p><code class="docutils literal notranslate"><span class="pre">from</span> <span class="pre">__future__</span> <span class="pre">import</span> <span class="pre">annotations</span></code> was previously scheduled to
become mandatory in Python 3.10, but the change was delayed and ultimately
canceled. This feature will eventually be deprecated and removed. See
<span class="target" id="index-10"></span><a class="pep reference external" href="https://peps.python.org/pep-0649/"><strong>PEP 649</strong></a> and <span class="target" id="index-11"></span><a class="pep reference external" href="https://peps.python.org/pep-0749/"><strong>PEP 749</strong></a>.</p>
</aside>
</aside>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<dl class="simple">
<dt><a class="reference internal" href="../reference/simple_stmts.html#future"><span class="std std-ref">Future statements</span></a></dt><dd><p>How the compiler treats future imports.</p>
</dd>
<dt><span class="target" id="index-12"></span><a class="pep reference external" href="https://peps.python.org/pep-0236/"><strong>PEP 236</strong></a> - Back to the __future__</dt><dd><p>The original proposal for the __future__ mechanism.</p>
</dd>
</dl>
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