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class="sidebar-title">Hello World!</p>212<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>213 214<span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">main</span><span class="p">():</span>215    <span class="nb">print</span><span class="p">(</span><span class="s1">&#39;Hello ...&#39;</span><span class="p">)</span>216    <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>217    <span class="nb">print</span><span class="p">(</span><span class="s1">&#39;... World!&#39;</span><span class="p">)</span>218 219<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>220</pre></div>221</div>222</aside>223<p>asyncio is a library to write <strong>concurrent</strong> code using224the <strong>async/await</strong> syntax.</p>225<p>asyncio is used as a foundation for multiple Python asynchronous226frameworks that provide high-performance network and web-servers,227database connection libraries, distributed task queues, etc.</p>228<p>asyncio is often a perfect fit for IO-bound and high-level229<strong>structured</strong> network code.</p>230<div class="admonition seealso">231<p class="admonition-title">See also</p>232<dl class="simple">233<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>234</dd>235</dl>236</div>237<p>asyncio provides a set of <strong>high-level</strong> APIs to:</p>238<ul class="simple">239<li><p><a class="reference internal" href="asyncio-task.html#coroutine"><span class="std std-ref">run Python coroutines</span></a> concurrently and240have full control over their execution;</p></li>241<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>242<li><p>control <a class="reference internal" href="asyncio-subprocess.html#asyncio-subprocess"><span class="std std-ref">subprocesses</span></a>;</p></li>243<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>244<li><p><a class="reference internal" href="asyncio-sync.html#asyncio-sync"><span class="std std-ref">synchronize</span></a> concurrent code;</p></li>245</ul>246<p>Additionally, there are <strong>low-level</strong> APIs for247<em>library and framework developers</em> to:</p>248<ul class="simple">249<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>, which250provide asynchronous APIs for <a class="reference internal" href="asyncio-eventloop.html#loop-create-server"><span class="std std-ref">networking</span></a>,251running <a class="reference internal" href="asyncio-eventloop.html#loop-subprocess-exec"><span class="std std-ref">subprocesses</span></a>,252handling <a class="reference internal" href="asyncio-eventloop.html#loop-add-signal-handler"><span class="std std-ref">OS signals</span></a>, etc;</p></li>253<li><p>implement efficient protocols using254<a class="reference internal" href="asyncio-protocol.html#asyncio-transports-protocols"><span class="std std-ref">transports</span></a>;</p></li>255<li><p><a class="reference internal" href="asyncio-future.html#asyncio-futures"><span class="std std-ref">bridge</span></a> callback-based libraries and code256with async/await syntax.</p></li>257</ul>258<div class="availability docutils container">259<p><a class="reference internal" href="intro.html#availability"><span class="std std-ref">Availability</span></a>: not WASI.</p>260<p>This module does not work or is not available on WebAssembly. See261<a class="reference internal" href="intro.html#wasm-availability"><span class="std std-ref">WebAssembly platforms</span></a> for more information.</p>262</div>263<p class="rubric" id="asyncio-cli">asyncio REPL</p>264<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>265<div class="highlight-pycon notranslate"><div class="highlight"><pre><span></span><span class="go">$ python -m asyncio</span>266<span class="go">asyncio REPL ...</span>267<span class="go">Use &quot;await&quot; directly instead of &quot;asyncio.run()&quot;.</span>268<span class="go">Type &quot;help&quot;, &quot;copyright&quot;, &quot;credits&quot; or &quot;license&quot; for more information.</span>269<span class="gp">&gt;&gt;&gt; </span><span class="kn">import</span><span class="w"> </span><span class="nn">asyncio</span>270<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>271<span class="go">&#39;hello&#39;</span>272</pre></div>273</div>274<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>.275It is recommended that the default REPL is used276for full functionality and the latest features.</p>277<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>278<div class="versionchanged">279<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)280Emits audit events.</p>281</div>282<div class="versionchanged">283<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> is284also executed. Emits audit events.</p>285</div>286<p class="rubric">Reference</p>287<div class="toctree-wrapper compound">288<p class="caption" role="heading"><span class="caption-text">High-level APIs</span></p>289<ul>290<li class="toctree-l1"><a class="reference internal" href="asyncio-runner.html">Runners</a></li>291<li class="toctree-l1"><a class="reference internal" href="asyncio-task.html">Coroutines and Tasks</a></li>292<li class="toctree-l1"><a class="reference internal" href="asyncio-stream.html">Streams</a></li>293<li class="toctree-l1"><a class="reference internal" href="asyncio-sync.html">Synchronization Primitives</a></li>294<li class="toctree-l1"><a class="reference internal" href="asyncio-subprocess.html">Subprocesses</a></li>295<li class="toctree-l1"><a class="reference internal" href="asyncio-queue.html">Queues</a></li>296<li class="toctree-l1"><a class="reference internal" href="asyncio-exceptions.html">Exceptions</a></li>297<li class="toctree-l1"><a class="reference internal" href="asyncio-graph.html">Call Graph Introspection</a></li>298</ul>299</div>300<div class="toctree-wrapper compound">301<p class="caption" role="heading"><span class="caption-text">Low-level APIs</span></p>302<ul>303<li class="toctree-l1"><a class="reference internal" href="asyncio-eventloop.html">Event Loop</a></li>304<li class="toctree-l1"><a class="reference internal" href="asyncio-future.html">Futures</a></li>305<li class="toctree-l1"><a class="reference internal" href="asyncio-protocol.html">Transports and Protocols</a></li>306<li class="toctree-l1"><a class="reference internal" href="asyncio-policy.html">Policies</a></li>307<li class="toctree-l1"><a class="reference internal" href="asyncio-platforms.html">Platform Support</a></li>308<li class="toctree-l1"><a class="reference internal" href="asyncio-extending.html">Extending</a></li>309</ul>310</div>311<div class="toctree-wrapper compound">312<p class="caption" role="heading"><span class="caption-text">Guides and Tutorials</span></p>313<ul>314<li class="toctree-l1"><a class="reference internal" href="asyncio-api-index.html">High-level API Index</a></li>315<li class="toctree-l1"><a class="reference internal" href="asyncio-llapi-index.html">Low-level API Index</a></li>316<li class="toctree-l1"><a class="reference internal" href="asyncio-dev.html">Developing with asyncio</a></li>317</ul>318</div>319<div class="admonition note">320<p class="admonition-title">Note</p>321<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>322</div>323</section>324 325 326            <div class="clearer"></div>327          </div>328        </div>329      </div>330      <div class="sphinxsidebar" role="navigation" aria-label="Main">331        <div class="sphinxsidebarwrapper">332  <div>333    <h4>Previous topic</h4>334    <p class="topless"><a href="ipc.html"335                          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