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<span id="asyncio-platform-support"></span><h1>Platform Support<a class="headerlink" href="#platform-support" title="Permalink to this headline">¶</a></h1>
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<p>The <a class="reference internal" href="asyncio.html#module-asyncio" title="asyncio: Asynchronous I/O."><code class="xref py py-mod docutils literal notranslate"><span class="pre">asyncio</span></code></a> module is designed to be portable,
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but some platforms have subtle differences and limitations
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due to the platforms’ underlying architecture and capabilities.</p>
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<div class="section" id="all-platforms">
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<h2>All Platforms<a class="headerlink" href="#all-platforms" title="Permalink to this headline">¶</a></h2>
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<ul class="simple">
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<li><p><a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.add_reader" title="asyncio.loop.add_reader"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.add_reader()</span></code></a> and <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.add_writer" title="asyncio.loop.add_writer"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.add_writer()</span></code></a>
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cannot be used to monitor file I/O.</p></li>
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</ul>
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<div class="section" id="windows">
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<h2>Windows<a class="headerlink" href="#windows" title="Permalink to this headline">¶</a></h2>
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<p>All event loops on Windows do not support the following methods:</p>
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<ul class="simple">
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<li><p><a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.create_unix_connection" title="asyncio.loop.create_unix_connection"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_unix_connection()</span></code></a> and
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<a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.create_unix_server" title="asyncio.loop.create_unix_server"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_unix_server()</span></code></a> are not supported.
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The <a class="reference internal" href="socket.html#socket.AF_UNIX" title="socket.AF_UNIX"><code class="xref py py-data docutils literal notranslate"><span class="pre">socket.AF_UNIX</span></code></a> socket family is specific to Unix.</p></li>
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<li><p><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">loop.add_signal_handler()</span></code></a> and
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<a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.remove_signal_handler" title="asyncio.loop.remove_signal_handler"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.remove_signal_handler()</span></code></a> are not supported.</p></li>
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</ul>
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<p><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> has the following limitations:</p>
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<ul class="simple">
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<li><p><a class="reference internal" href="selectors.html#selectors.SelectSelector" title="selectors.SelectSelector"><code class="xref py py-class docutils literal notranslate"><span class="pre">SelectSelector</span></code></a> is used to wait on socket events:
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it supports sockets and is limited to 512 sockets.</p></li>
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<li><p><a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.add_reader" title="asyncio.loop.add_reader"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.add_reader()</span></code></a> and <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.add_writer" title="asyncio.loop.add_writer"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.add_writer()</span></code></a> only accept
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socket handles (e.g. pipe file descriptors are not supported).</p></li>
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<li><p>Pipes are not supported, so the <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.connect_read_pipe" title="asyncio.loop.connect_read_pipe"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.connect_read_pipe()</span></code></a>
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and <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.connect_write_pipe" title="asyncio.loop.connect_write_pipe"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.connect_write_pipe()</span></code></a> methods are not implemented.</p></li>
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<li><p><a class="reference internal" href="asyncio-subprocess.html#asyncio-subprocess"><span class="std std-ref">Subprocesses</span></a> are not supported, i.e.
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<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">loop.subprocess_exec()</span></code></a> and <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.subprocess_shell" title="asyncio.loop.subprocess_shell"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.subprocess_shell()</span></code></a>
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methods are not implemented.</p></li>
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</ul>
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<p><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> has the following limitations:</p>
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<ul class="simple">
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<li><p>The <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.create_datagram_endpoint" title="asyncio.loop.create_datagram_endpoint"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_datagram_endpoint()</span></code></a> method
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is not supported.</p></li>
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<li><p>The <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.add_reader" title="asyncio.loop.add_reader"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.add_reader()</span></code></a> and <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.add_writer" title="asyncio.loop.add_writer"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.add_writer()</span></code></a>
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methods are not supported.</p></li>
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</ul>
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<p>The resolution of the monotonic clock on Windows is usually around 15.6
|
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msec. The best resolution is 0.5 msec. The resolution depends on the
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hardware (availability of <a class="reference external" href="https://en.wikipedia.org/wiki/High_Precision_Event_Timer">HPET</a>) and on the
|
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Windows configuration.</p>
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<div class="section" id="subprocess-support-on-windows">
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<span id="asyncio-windows-subprocess"></span><h3>Subprocess Support on Windows<a class="headerlink" href="#subprocess-support-on-windows" title="Permalink to this headline">¶</a></h3>
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<p><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 Windows does not support subproceses.
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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> should be used instead:</p>
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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="n">asyncio</span><span class="o">.</span><span class="n">set_event_loop_policy</span><span class="p">(</span>
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<span class="n">asyncio</span><span class="o">.</span><span class="n">WindowsProactorEventLoopPolicy</span><span class="p">())</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">your_code</span><span class="p">())</span>
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</pre></div>
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</div>
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<p>The <a class="reference internal" href="asyncio-policy.html#asyncio.AbstractEventLoopPolicy.set_child_watcher" title="asyncio.AbstractEventLoopPolicy.set_child_watcher"><code class="xref py py-meth docutils literal notranslate"><span class="pre">policy.set_child_watcher()</span></code></a> function is also
|
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not supported, as <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> has a different mechanism
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to watch child processes.</p>
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</div>
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</div>
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<div class="section" id="macos">
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<h2>macOS<a class="headerlink" href="#macos" title="Permalink to this headline">¶</a></h2>
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<p>Modern macOS versions are fully supported.</p>
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<p class="rubric">macOS <= 10.8</p>
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<p>On macOS 10.6, 10.7 and 10.8, the default event loop
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uses <a class="reference internal" href="selectors.html#selectors.KqueueSelector" title="selectors.KqueueSelector"><code class="xref py py-class docutils literal notranslate"><span class="pre">selectors.KqueueSelector</span></code></a>, which does not support
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character devices on these versions. 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>
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can be manually configured to use <a class="reference internal" href="selectors.html#selectors.SelectSelector" title="selectors.SelectSelector"><code class="xref py py-class docutils literal notranslate"><span class="pre">SelectSelector</span></code></a>
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or <a class="reference internal" href="selectors.html#selectors.PollSelector" title="selectors.PollSelector"><code class="xref py py-class docutils literal notranslate"><span class="pre">PollSelector</span></code></a> to support character devices on
|
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these older versions of macOS. Example:</p>
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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="kn">import</span> <span class="nn">selectors</span>
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<span class="n">selector</span> <span class="o">=</span> <span class="n">selectors</span><span class="o">.</span><span class="n">SelectSelector</span><span class="p">()</span>
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<span class="n">loop</span> <span class="o">=</span> <span class="n">asyncio</span><span class="o">.</span><span class="n">SelectorEventLoop</span><span class="p">(</span><span class="n">selector</span><span class="p">)</span>
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<span class="n">asyncio</span><span class="o">.</span><span class="n">set_event_loop</span><span class="p">(</span><span class="n">loop</span><span class="p">)</span>
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</pre></div>
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<h3><a href="../contents.html">Table of Contents</a></h3>
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<li><a class="reference internal" href="#">Platform Support</a><ul>
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<li><a class="reference internal" href="#all-platforms">All Platforms</a></li>
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<li><a class="reference internal" href="#windows">Windows</a><ul>
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<li><a class="reference internal" href="#subprocess-support-on-windows">Subprocess Support on Windows</a></li>
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</ul>
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</li>
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<li><a class="reference internal" href="#macos">macOS</a></li>
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The Python Software Foundation is a non-profit corporation.
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<a href="https://www.python.org/psf/donations/">Please donate.</a>
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<br />
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Last updated on Jul 13, 2019.
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<a href="../bugs.html">Found a bug</a>?
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<br />
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Created using <a href="http://sphinx.pocoo.org/">Sphinx</a> 2.0.1.
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