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| <li><a class="reference internal" href="#">Policies</a><ul> | |
| <li><a class="reference internal" href="#getting-and-setting-the-policy">Getting and Setting the Policy</a></li> | |
| <li><a class="reference internal" href="#policy-objects">Policy Objects</a></li> | |
| <li><a class="reference internal" href="#custom-policies">Custom Policies</a></li> | |
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| <section id="policies"> | |
| <span id="asyncio-policies"></span><h1>Policies<a class="headerlink" href="#policies" title="Link to this heading">¶</a></h1> | |
| <div class="admonition warning"> | |
| <p class="admonition-title">Warning</p> | |
| <p>Policies are deprecated and will be removed in Python 3.16. | |
| Users are encouraged to use the <a class="reference internal" href="asyncio-runner.html#asyncio.run" title="asyncio.run"><code class="xref py py-func docutils literal notranslate"><span class="pre">asyncio.run()</span></code></a> function | |
| or the <a class="reference internal" href="asyncio-runner.html#asyncio.Runner" title="asyncio.Runner"><code class="xref py py-class docutils literal notranslate"><span class="pre">asyncio.Runner</span></code></a> with <em>loop_factory</em> to use | |
| the desired loop implementation.</p> | |
| </div> | |
| <p>An event loop policy is a global object | |
| used to get and set the current <a class="reference internal" href="asyncio-eventloop.html#asyncio-event-loop"><span class="std std-ref">event loop</span></a>, | |
| as well as create new event loops. | |
| The default policy can be <a class="reference internal" href="#asyncio-policy-get-set"><span class="std std-ref">replaced</span></a> with | |
| <a class="reference internal" href="#asyncio-policy-builtin"><span class="std std-ref">built-in alternatives</span></a> | |
| to use different event loop implementations, | |
| or substituted by a <a class="reference internal" href="#asyncio-custom-policies"><span class="std std-ref">custom policy</span></a> | |
| that can override these behaviors.</p> | |
| <p>The <a class="reference internal" href="#asyncio-policy-objects"><span class="std std-ref">policy object</span></a> | |
| gets and sets a separate event loop per <em>context</em>. | |
| This is per-thread by default, | |
| though custom policies could define <em>context</em> differently.</p> | |
| <p>Custom event loop policies can control the behavior of | |
| <a class="reference internal" href="asyncio-eventloop.html#asyncio.get_event_loop" title="asyncio.get_event_loop"><code class="xref py py-func docutils literal notranslate"><span class="pre">get_event_loop()</span></code></a>, <a class="reference internal" href="asyncio-eventloop.html#asyncio.set_event_loop" title="asyncio.set_event_loop"><code class="xref py py-func docutils literal notranslate"><span class="pre">set_event_loop()</span></code></a>, and <a class="reference internal" href="asyncio-eventloop.html#asyncio.new_event_loop" title="asyncio.new_event_loop"><code class="xref py py-func docutils literal notranslate"><span class="pre">new_event_loop()</span></code></a>.</p> | |
| <p>Policy objects should implement the APIs defined | |
| in the <a class="reference internal" href="#asyncio.AbstractEventLoopPolicy" title="asyncio.AbstractEventLoopPolicy"><code class="xref py py-class docutils literal notranslate"><span class="pre">AbstractEventLoopPolicy</span></code></a> abstract base class.</p> | |
| <section id="getting-and-setting-the-policy"> | |
| <span id="asyncio-policy-get-set"></span><h2>Getting and Setting the Policy<a class="headerlink" href="#getting-and-setting-the-policy" title="Link to this heading">¶</a></h2> | |
| <p>The following functions can be used to get and set the policy | |
| for the current process:</p> | |
| <dl class="py function"> | |
| <dt class="sig sig-object py" id="asyncio.get_event_loop_policy"> | |
| <span class="sig-prename descclassname"><span class="pre">asyncio.</span></span><span class="sig-name descname"><span class="pre">get_event_loop_policy</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.get_event_loop_policy" title="Link to this definition">¶</a></dt> | |
| <dd><p>Return the current process-wide policy.</p> | |
| <div class="deprecated"> | |
| <p><span class="versionmodified deprecated">Deprecated since version 3.14: </span>The <code class="xref py py-func docutils literal notranslate"><span class="pre">get_event_loop_policy()</span></code> function is deprecated and | |
| will be removed in Python 3.16.</p> | |
| </div> | |
| </dd></dl> | |
| <dl class="py function"> | |
| <dt class="sig sig-object py" id="asyncio.set_event_loop_policy"> | |
| <span class="sig-prename descclassname"><span class="pre">asyncio.</span></span><span class="sig-name descname"><span class="pre">set_event_loop_policy</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">policy</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.set_event_loop_policy" title="Link to this definition">¶</a></dt> | |
| <dd><p>Set the current process-wide policy to <em>policy</em>.</p> | |
| <p>If <em>policy</em> is set to <code class="docutils literal notranslate"><span class="pre">None</span></code>, the default policy is restored.</p> | |
| <div class="deprecated"> | |
| <p><span class="versionmodified deprecated">Deprecated since version 3.14: </span>The <code class="xref py py-func docutils literal notranslate"><span class="pre">set_event_loop_policy()</span></code> function is deprecated and | |
| will be removed in Python 3.16.</p> | |
| </div> | |
| </dd></dl> | |
| </section> | |
| <section id="policy-objects"> | |
| <span id="asyncio-policy-objects"></span><h2>Policy Objects<a class="headerlink" href="#policy-objects" title="Link to this heading">¶</a></h2> | |
| <p>The abstract event loop policy base class is defined as follows:</p> | |
| <dl class="py class"> | |
| <dt class="sig sig-object py" id="asyncio.AbstractEventLoopPolicy"> | |
| <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">asyncio.</span></span><span class="sig-name descname"><span class="pre">AbstractEventLoopPolicy</span></span><a class="headerlink" href="#asyncio.AbstractEventLoopPolicy" title="Link to this definition">¶</a></dt> | |
| <dd><p>An abstract base class for asyncio policies.</p> | |
| <dl class="py method"> | |
| <dt class="sig sig-object py" id="asyncio.AbstractEventLoopPolicy.get_event_loop"> | |
| <span class="sig-name descname"><span class="pre">get_event_loop</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.AbstractEventLoopPolicy.get_event_loop" title="Link to this definition">¶</a></dt> | |
| <dd><p>Get the event loop for the current context.</p> | |
| <p>Return an event loop object implementing the | |
| <a class="reference internal" href="asyncio-eventloop.html#asyncio.AbstractEventLoop" title="asyncio.AbstractEventLoop"><code class="xref py py-class docutils literal notranslate"><span class="pre">AbstractEventLoop</span></code></a> interface.</p> | |
| <p>This method should never return <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p> | |
| <div class="versionchanged"> | |
| <p><span class="versionmodified changed">Changed in version 3.6.</span></p> | |
| </div> | |
| </dd></dl> | |
| <dl class="py method"> | |
| <dt class="sig sig-object py" id="asyncio.AbstractEventLoopPolicy.set_event_loop"> | |
| <span class="sig-name descname"><span class="pre">set_event_loop</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">loop</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.AbstractEventLoopPolicy.set_event_loop" title="Link to this definition">¶</a></dt> | |
| <dd><p>Set the event loop for the current context to <em>loop</em>.</p> | |
| </dd></dl> | |
| <dl class="py method"> | |
| <dt class="sig sig-object py" id="asyncio.AbstractEventLoopPolicy.new_event_loop"> | |
| <span class="sig-name descname"><span class="pre">new_event_loop</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.AbstractEventLoopPolicy.new_event_loop" title="Link to this definition">¶</a></dt> | |
| <dd><p>Create and return a new event loop object.</p> | |
| <p>This method should never return <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p> | |
| </dd></dl> | |
| <div class="deprecated"> | |
| <p><span class="versionmodified deprecated">Deprecated since version 3.14: </span>The <code class="xref py py-class docutils literal notranslate"><span class="pre">AbstractEventLoopPolicy</span></code> class is deprecated and | |
| will be removed in Python 3.16.</p> | |
| </div> | |
| </dd></dl> | |
| <p id="asyncio-policy-builtin">asyncio ships with the following built-in policies:</p> | |
| <dl class="py class"> | |
| <dt class="sig sig-object py" id="asyncio.DefaultEventLoopPolicy"> | |
| <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">asyncio.</span></span><span class="sig-name descname"><span class="pre">DefaultEventLoopPolicy</span></span><a class="headerlink" href="#asyncio.DefaultEventLoopPolicy" title="Link to this definition">¶</a></dt> | |
| <dd><p>The default asyncio policy. Uses <a class="reference internal" href="asyncio-eventloop.html#asyncio.SelectorEventLoop" title="asyncio.SelectorEventLoop"><code class="xref py py-class docutils literal notranslate"><span class="pre">SelectorEventLoop</span></code></a> | |
| on Unix and <a class="reference internal" href="asyncio-eventloop.html#asyncio.ProactorEventLoop" title="asyncio.ProactorEventLoop"><code class="xref py py-class docutils literal notranslate"><span class="pre">ProactorEventLoop</span></code></a> on Windows.</p> | |
| <p>There is no need to install the default policy manually. asyncio | |
| is configured to use the default policy automatically.</p> | |
| <div class="versionchanged"> | |
| <p><span class="versionmodified changed">Changed in version 3.8: </span>On Windows, <a class="reference internal" href="asyncio-eventloop.html#asyncio.ProactorEventLoop" title="asyncio.ProactorEventLoop"><code class="xref py py-class docutils literal notranslate"><span class="pre">ProactorEventLoop</span></code></a> is now used by default.</p> | |
| </div> | |
| <div class="versionchanged"> | |
| <p><span class="versionmodified changed">Changed in version 3.14: </span>The <a class="reference internal" href="asyncio-eventloop.html#asyncio.get_event_loop" title="asyncio.get_event_loop"><code class="xref py py-meth docutils literal notranslate"><span class="pre">get_event_loop()</span></code></a> method of the default asyncio policy now | |
| raises a <a class="reference internal" href="exceptions.html#RuntimeError" title="RuntimeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">RuntimeError</span></code></a> if there is no set event loop.</p> | |
| </div> | |
| <div class="deprecated"> | |
| <p><span class="versionmodified deprecated">Deprecated since version 3.14: </span>The <code class="xref py py-class docutils literal notranslate"><span class="pre">DefaultEventLoopPolicy</span></code> class is deprecated and | |
| will be removed in Python 3.16.</p> | |
| </div> | |
| </dd></dl> | |
| <dl class="py class"> | |
| <dt class="sig sig-object py" id="asyncio.WindowsSelectorEventLoopPolicy"> | |
| <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">asyncio.</span></span><span class="sig-name descname"><span class="pre">WindowsSelectorEventLoopPolicy</span></span><a class="headerlink" href="#asyncio.WindowsSelectorEventLoopPolicy" title="Link to this definition">¶</a></dt> | |
| <dd><p>An alternative event loop policy that uses the | |
| <a class="reference internal" href="asyncio-eventloop.html#asyncio.SelectorEventLoop" title="asyncio.SelectorEventLoop"><code class="xref py py-class docutils literal notranslate"><span class="pre">SelectorEventLoop</span></code></a> event loop implementation.</p> | |
| <div class="availability docutils container"> | |
| <p><a class="reference internal" href="intro.html#availability"><span class="std std-ref">Availability</span></a>: Windows.</p> | |
| </div> | |
| <div class="deprecated"> | |
| <p><span class="versionmodified deprecated">Deprecated since version 3.14: </span>The <code class="xref py py-class docutils literal notranslate"><span class="pre">WindowsSelectorEventLoopPolicy</span></code> class is deprecated and | |
| will be removed in Python 3.16.</p> | |
| </div> | |
| </dd></dl> | |
| <dl class="py class"> | |
| <dt class="sig sig-object py" id="asyncio.WindowsProactorEventLoopPolicy"> | |
| <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">asyncio.</span></span><span class="sig-name descname"><span class="pre">WindowsProactorEventLoopPolicy</span></span><a class="headerlink" href="#asyncio.WindowsProactorEventLoopPolicy" title="Link to this definition">¶</a></dt> | |
| <dd><p>An alternative event loop policy that uses the | |
| <a class="reference internal" href="asyncio-eventloop.html#asyncio.ProactorEventLoop" title="asyncio.ProactorEventLoop"><code class="xref py py-class docutils literal notranslate"><span class="pre">ProactorEventLoop</span></code></a> event loop implementation.</p> | |
| <div class="availability docutils container"> | |
| <p><a class="reference internal" href="intro.html#availability"><span class="std std-ref">Availability</span></a>: Windows.</p> | |
| </div> | |
| <div class="deprecated"> | |
| <p><span class="versionmodified deprecated">Deprecated since version 3.14: </span>The <code class="xref py py-class docutils literal notranslate"><span class="pre">WindowsProactorEventLoopPolicy</span></code> class is deprecated and | |
| will be removed in Python 3.16.</p> | |
| </div> | |
| </dd></dl> | |
| </section> | |
| <section id="custom-policies"> | |
| <span id="asyncio-custom-policies"></span><h2>Custom Policies<a class="headerlink" href="#custom-policies" title="Link to this heading">¶</a></h2> | |
| <p>To implement a new event loop policy, it is recommended to subclass | |
| <a class="reference internal" href="#asyncio.DefaultEventLoopPolicy" title="asyncio.DefaultEventLoopPolicy"><code class="xref py py-class docutils literal notranslate"><span class="pre">DefaultEventLoopPolicy</span></code></a> and override the methods for which | |
| custom behavior is wanted, e.g.:</p> | |
| <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">class</span><span class="w"> </span><span class="nc">MyEventLoopPolicy</span><span class="p">(</span><span class="n">asyncio</span><span class="o">.</span><span class="n">DefaultEventLoopPolicy</span><span class="p">):</span> | |
| <span class="k">def</span><span class="w"> </span><span class="nf">get_event_loop</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span> | |
| <span class="w"> </span><span class="sd">"""Get the event loop.</span> | |
| <span class="sd"> This may be None or an instance of EventLoop.</span> | |
| <span class="sd"> """</span> | |
| <span class="n">loop</span> <span class="o">=</span> <span class="nb">super</span><span class="p">()</span><span class="o">.</span><span class="n">get_event_loop</span><span class="p">()</span> | |
| <span class="c1"># Do something with loop ...</span> | |
| <span class="k">return</span> <span class="n">loop</span> | |
| <span class="n">asyncio</span><span class="o">.</span><span class="n">set_event_loop_policy</span><span class="p">(</span><span class="n">MyEventLoopPolicy</span><span class="p">())</span> | |
| </pre></div> | |
| </div> | |
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| <li><a class="reference internal" href="#">Policies</a><ul> | |
| <li><a class="reference internal" href="#getting-and-setting-the-policy">Getting and Setting the Policy</a></li> | |
| <li><a class="reference internal" href="#policy-objects">Policy Objects</a></li> | |
| <li><a class="reference internal" href="#custom-policies">Custom Policies</a></li> | |
| </ul> | |
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