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  <section id="module-asyncio">
<span id="asyncio-asynchronous-i-o"></span><h1><code class="xref py py-mod docutils literal notranslate"><span class="pre">asyncio</span></code> — Asynchronous I/O<a class="headerlink" href="#module-asyncio" title="Link to this heading">¶</a></h1>
<hr class="docutils" />
<aside class="sidebar">
<p class="sidebar-title">Hello World!</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span><span class="w"> </span><span class="nn">asyncio</span>

<span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">main</span><span class="p">():</span>
    <span class="nb">print</span><span class="p">(</span><span class="s1">&#39;Hello ...&#39;</span><span class="p">)</span>
    <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>
    <span class="nb">print</span><span class="p">(</span><span class="s1">&#39;... World!&#39;</span><span class="p">)</span>

<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>
</pre></div>
</div>
</aside>
<p>asyncio is a library to write <strong>concurrent</strong> code using
the <strong>async/await</strong> syntax.</p>
<p>asyncio is used as a foundation for multiple Python asynchronous
frameworks that provide high-performance network and web-servers,
database connection libraries, distributed task queues, etc.</p>
<p>asyncio is often a perfect fit for IO-bound and high-level
<strong>structured</strong> network code.</p>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<dl class="simple">
<dt><a class="reference internal" href="../howto/a-conceptual-overview-of-asyncio.html#a-conceptual-overview-of-asyncio"><span class="std std-ref">A conceptual overview of asyncio</span></a></dt><dd><p>Explanation of the fundamentals of asyncio.</p>
</dd>
</dl>
</div>
<p>asyncio provides a set of <strong>high-level</strong> APIs to:</p>
<ul class="simple">
<li><p><a class="reference internal" href="asyncio-task.html#coroutine"><span class="std std-ref">run Python coroutines</span></a> concurrently and
have full control over their execution;</p></li>
<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>
<li><p>control <a class="reference internal" href="asyncio-subprocess.html#asyncio-subprocess"><span class="std std-ref">subprocesses</span></a>;</p></li>
<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>
<li><p><a class="reference internal" href="asyncio-sync.html#asyncio-sync"><span class="std std-ref">synchronize</span></a> concurrent code;</p></li>
</ul>
<p>Additionally, there are <strong>low-level</strong> APIs for
<em>library and framework developers</em> to:</p>
<ul class="simple">
<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
provide asynchronous APIs for <a class="reference internal" href="asyncio-eventloop.html#loop-create-server"><span class="std std-ref">networking</span></a>,
running <a class="reference internal" href="asyncio-eventloop.html#loop-subprocess-exec"><span class="std std-ref">subprocesses</span></a>,
handling <a class="reference internal" href="asyncio-eventloop.html#loop-add-signal-handler"><span class="std std-ref">OS signals</span></a>, etc;</p></li>
<li><p>implement efficient protocols using
<a class="reference internal" href="asyncio-protocol.html#asyncio-transports-protocols"><span class="std std-ref">transports</span></a>;</p></li>
<li><p><a class="reference internal" href="asyncio-future.html#asyncio-futures"><span class="std std-ref">bridge</span></a> callback-based libraries and code
with async/await syntax.</p></li>
</ul>
<div class="availability docutils container">
<p><a class="reference internal" href="intro.html#availability"><span class="std std-ref">Availability</span></a>: not WASI.</p>
<p>This module does not work or is not available on WebAssembly. See
<a class="reference internal" href="intro.html#wasm-availability"><span class="std std-ref">WebAssembly platforms</span></a> for more information.</p>
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<p class="rubric" id="asyncio-cli">asyncio REPL</p>
<p>You can experiment with an <code class="docutils literal notranslate"><span class="pre">asyncio</span></code> concurrent context in the <a class="reference internal" href="../glossary.html#term-REPL"><span class="xref std std-term">REPL</span></a>:</p>
<div class="highlight-pycon notranslate"><div class="highlight"><pre><span></span><span class="go">$ python -m asyncio</span>
<span class="go">asyncio REPL ...</span>
<span class="go">Use &quot;await&quot; directly instead of &quot;asyncio.run()&quot;.</span>
<span class="go">Type &quot;help&quot;, &quot;copyright&quot;, &quot;credits&quot; or &quot;license&quot; for more information.</span>
<span class="gp">&gt;&gt;&gt; </span><span class="kn">import</span><span class="w"> </span><span class="nn">asyncio</span>
<span class="gp">&gt;&gt;&gt; </span><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">10</span><span class="p">,</span> <span class="n">result</span><span class="o">=</span><span class="s1">&#39;hello&#39;</span><span class="p">)</span>
<span class="go">&#39;hello&#39;</span>
</pre></div>
</div>
<p>This REPL provides limited compatibility with <span class="target" id="index-0"></span><a class="reference internal" href="../using/cmdline.html#envvar-PYTHON_BASIC_REPL"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHON_BASIC_REPL</span></code></a>.
It is recommended that the default REPL is used
for full functionality and the latest features.</p>
<p class="audit-hook" id="audit_event_cpython_run_stdin_2">Raises an <a class="reference internal" href="sys.html#auditing"><span class="std std-ref">auditing event</span></a> <code class="docutils literal notranslate"><span class="pre">cpython.run_stdin</span></code> with no arguments.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.12.5: </span>(also 3.11.10, 3.10.15, 3.9.20, and 3.8.20)
Emits audit events.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.13: </span>Uses PyREPL if possible, in which case <span class="target" id="index-1"></span><a class="reference internal" href="../using/cmdline.html#envvar-PYTHONSTARTUP"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONSTARTUP</span></code></a> is
also executed. Emits audit events.</p>
</div>
<p class="rubric">Reference</p>
<div class="toctree-wrapper compound">
<p class="caption" role="heading"><span class="caption-text">High-level APIs</span></p>
<ul>
<li class="toctree-l1"><a class="reference internal" href="asyncio-runner.html">Runners</a></li>
<li class="toctree-l1"><a class="reference internal" href="asyncio-task.html">Coroutines and Tasks</a></li>
<li class="toctree-l1"><a class="reference internal" href="asyncio-stream.html">Streams</a></li>
<li class="toctree-l1"><a class="reference internal" href="asyncio-sync.html">Synchronization Primitives</a></li>
<li class="toctree-l1"><a class="reference internal" href="asyncio-subprocess.html">Subprocesses</a></li>
<li class="toctree-l1"><a class="reference internal" href="asyncio-queue.html">Queues</a></li>
<li class="toctree-l1"><a class="reference internal" href="asyncio-exceptions.html">Exceptions</a></li>
<li class="toctree-l1"><a class="reference internal" href="asyncio-graph.html">Call Graph Introspection</a></li>
</ul>
</div>
<div class="toctree-wrapper compound">
<p class="caption" role="heading"><span class="caption-text">Low-level APIs</span></p>
<ul>
<li class="toctree-l1"><a class="reference internal" href="asyncio-eventloop.html">Event Loop</a></li>
<li class="toctree-l1"><a class="reference internal" href="asyncio-future.html">Futures</a></li>
<li class="toctree-l1"><a class="reference internal" href="asyncio-protocol.html">Transports and Protocols</a></li>
<li class="toctree-l1"><a class="reference internal" href="asyncio-policy.html">Policies</a></li>
<li class="toctree-l1"><a class="reference internal" href="asyncio-platforms.html">Platform Support</a></li>
<li class="toctree-l1"><a class="reference internal" href="asyncio-extending.html">Extending</a></li>
</ul>
</div>
<div class="toctree-wrapper compound">
<p class="caption" role="heading"><span class="caption-text">Guides and Tutorials</span></p>
<ul>
<li class="toctree-l1"><a class="reference internal" href="asyncio-api-index.html">High-level API Index</a></li>
<li class="toctree-l1"><a class="reference internal" href="asyncio-llapi-index.html">Low-level API Index</a></li>
<li class="toctree-l1"><a class="reference internal" href="asyncio-dev.html">Developing with asyncio</a></li>
</ul>
</div>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>The source code for asyncio can be found in <a class="extlink-source reference external" href="https://github.com/python/cpython/tree/main/Lib/asyncio/">Lib/asyncio/</a>.</p>
</div>
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