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<span id="asyncio-asynchronous-i-o"></span><h1><a class="reference internal" href="#module-asyncio" title="asyncio: Asynchronous I/O."><code class="xref py py-mod docutils literal notranslate"><span class="pre">asyncio</span></code></a> — Asynchronous I/O<a class="headerlink" href="#module-asyncio" title="Permalink to this headline">¶</a></h1>
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<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">asyncio</span>
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<span class="k">async</span> <span class="k">def</span> <span class="nf">main</span><span class="p">():</span>
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<span class="nb">print</span><span class="p">(</span><span class="s1">'Hello ...'</span><span class="p">)</span>
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<span class="k">await</span> <span class="n">asyncio</span><span class="o">.</span><span class="n">sleep</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
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<span class="nb">print</span><span class="p">(</span><span class="s1">'... World!'</span><span class="p">)</span>
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<span class="c1"># Python 3.7+</span>
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<span class="n">asyncio</span><span class="o">.</span><span class="n">run</span><span class="p">(</span><span class="n">main</span><span class="p">())</span>
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</pre></div>
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</div>
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</div>
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<p>asyncio is a library to write <strong>concurrent</strong> code using
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the <strong>async/await</strong> syntax.</p>
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<p>asyncio is used as a foundation for multiple Python asynchronous
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frameworks that provide high-performance network and web-servers,
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database connection libraries, distributed task queues, etc.</p>
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<p>asyncio is often a perfect fit for IO-bound and high-level
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<strong>structured</strong> network code.</p>
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<p>asyncio provides a set of <strong>high-level</strong> APIs to:</p>
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<ul class="simple">
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<li><p><a class="reference internal" href="asyncio-task.html#coroutine"><span class="std std-ref">run Python coroutines</span></a> concurrently and
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have full control over their execution;</p></li>
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<li><p>perform <a class="reference internal" href="asyncio-stream.html#asyncio-streams"><span class="std std-ref">network IO and IPC</span></a>;</p></li>
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<li><p>control <a class="reference internal" href="asyncio-subprocess.html#asyncio-subprocess"><span class="std std-ref">subprocesses</span></a>;</p></li>
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<li><p>distribute tasks via <a class="reference internal" href="asyncio-queue.html#asyncio-queues"><span class="std std-ref">queues</span></a>;</p></li>
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<li><p><a class="reference internal" href="asyncio-sync.html#asyncio-sync"><span class="std std-ref">synchronize</span></a> concurrent code;</p></li>
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</ul>
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<p>Additionally, there are <strong>low-level</strong> APIs for
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<em>library and framework developers</em> to:</p>
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<ul class="simple">
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<li><p>create and manage <a class="reference internal" href="asyncio-eventloop.html#asyncio-event-loop"><span class="std std-ref">event loops</span></a>, which
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provide asynchronous APIs for <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.create_server" title="asyncio.loop.create_server"><code class="xref py py-meth docutils literal notranslate"><span class="pre">networking</span></code></a>,
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running <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.subprocess_exec" title="asyncio.loop.subprocess_exec"><code class="xref py py-meth docutils literal notranslate"><span class="pre">subprocesses</span></code></a>,
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handling <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.add_signal_handler" title="asyncio.loop.add_signal_handler"><code class="xref py py-meth docutils literal notranslate"><span class="pre">OS</span> <span class="pre">signals</span></code></a>, etc;</p></li>
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<li><p>implement efficient protocols using
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<a class="reference internal" href="asyncio-protocol.html#asyncio-transports-protocols"><span class="std std-ref">transports</span></a>;</p></li>
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