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<h3><a href="../contents.html">Table of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">Event Loop</a><ul>
<li><a class="reference internal" href="#event-loop-methods">Event Loop Methods</a><ul>
<li><a class="reference internal" href="#running-and-stopping-the-loop">Running and stopping the loop</a></li>
<li><a class="reference internal" href="#scheduling-callbacks">Scheduling callbacks</a></li>
<li><a class="reference internal" href="#scheduling-delayed-callbacks">Scheduling delayed callbacks</a></li>
<li><a class="reference internal" href="#creating-futures-and-tasks">Creating Futures and Tasks</a></li>
<li><a class="reference internal" href="#opening-network-connections">Opening network connections</a></li>
<li><a class="reference internal" href="#creating-network-servers">Creating network servers</a></li>
<li><a class="reference internal" href="#transferring-files">Transferring files</a></li>
<li><a class="reference internal" href="#tls-upgrade">TLS Upgrade</a></li>
<li><a class="reference internal" href="#watching-file-descriptors">Watching file descriptors</a></li>
<li><a class="reference internal" href="#working-with-socket-objects-directly">Working with socket objects directly</a></li>
<li><a class="reference internal" href="#dns">DNS</a></li>
<li><a class="reference internal" href="#working-with-pipes">Working with pipes</a></li>
<li><a class="reference internal" href="#unix-signals">Unix signals</a></li>
<li><a class="reference internal" href="#executing-code-in-thread-or-process-pools">Executing code in thread or process pools</a></li>
<li><a class="reference internal" href="#error-handling-api">Error Handling API</a></li>
<li><a class="reference internal" href="#enabling-debug-mode">Enabling debug mode</a></li>
<li><a class="reference internal" href="#running-subprocesses">Running Subprocesses</a></li>
</ul>
</li>
<li><a class="reference internal" href="#callback-handles">Callback Handles</a></li>
<li><a class="reference internal" href="#server-objects">Server Objects</a></li>
<li><a class="reference internal" href="#event-loop-implementations">Event Loop Implementations</a></li>
<li><a class="reference internal" href="#examples">Examples</a><ul>
<li><a class="reference internal" href="#hello-world-with-call-soon">Hello World with call_soon()</a></li>
<li><a class="reference internal" href="#display-the-current-date-with-call-later">Display the current date with call_later()</a></li>
<li><a class="reference internal" href="#watch-a-file-descriptor-for-read-events">Watch a file descriptor for read events</a></li>
<li><a class="reference internal" href="#set-signal-handlers-for-sigint-and-sigterm">Set signal handlers for SIGINT and SIGTERM</a></li>
</ul>
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<section id="event-loop">
<span id="asyncio-event-loop"></span><h1>Event Loop<a class="headerlink" href="#event-loop" title="Link to this heading">¶</a></h1>
<p><strong>Source code:</strong> <a class="extlink-source reference external" href="https://github.com/python/cpython/tree/main/Lib/asyncio/events.py">Lib/asyncio/events.py</a>,
<a class="extlink-source reference external" href="https://github.com/python/cpython/tree/main/Lib/asyncio/base_events.py">Lib/asyncio/base_events.py</a></p>
<hr class="docutils" />
<p class="rubric">Preface</p>
<p>The event loop is the core of every asyncio application.
Event loops run asynchronous tasks and callbacks, perform network
IO operations, and run subprocesses.</p>
<p>Application developers should typically use the high-level asyncio functions,
such as <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>, and should rarely need to reference the loop
object or call its methods. This section is intended mostly for authors
of lower-level code, libraries, and frameworks, who need finer control over
the event loop behavior.</p>
<p class="rubric">Obtaining the Event Loop</p>
<p>The following low-level functions can be used to get, set, or create
an event loop:</p>
<dl class="py function">
<dt class="sig sig-object py" id="asyncio.get_running_loop">
<span class="sig-prename descclassname"><span class="pre">asyncio.</span></span><span class="sig-name descname"><span class="pre">get_running_loop</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.get_running_loop" title="Link to this definition">¶</a></dt>
<dd><p>Return the running event loop in the current OS thread.</p>
<p>Raise 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 running event loop.</p>
<p>This function can only be called from a coroutine or a callback.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.7.</span></p>
</div>
</dd></dl>
<dl class="py function">
<dt class="sig sig-object py" id="asyncio.get_event_loop">
<span class="sig-prename descclassname"><span class="pre">asyncio.</span></span><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.get_event_loop" title="Link to this definition">¶</a></dt>
<dd><p>Get the current event loop.</p>
<p>When called from a coroutine or a callback (e.g. scheduled with
call_soon or similar API), this function will always return the
running event loop.</p>
<p>If there is no running event loop set, the function will return
the result of the <code class="docutils literal notranslate"><span class="pre">get_event_loop_policy().get_event_loop()</span></code> call.</p>
<p>Because this function has rather complex behavior (especially
when custom event loop policies are in use), using the
<a class="reference internal" href="#asyncio.get_running_loop" title="asyncio.get_running_loop"><code class="xref py py-func docutils literal notranslate"><span class="pre">get_running_loop()</span></code></a> function is preferred to <code class="xref py py-func docutils literal notranslate"><span class="pre">get_event_loop()</span></code>
in coroutines and callbacks.</p>
<p>As noted above, consider using the higher-level <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,
instead of using these lower level functions to manually create and close an
event loop.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.14: </span>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 current event loop.</p>
</div>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>The <code class="xref py py-mod docutils literal notranslate"><span class="pre">asyncio</span></code> policy system is deprecated and will be removed
in Python 3.16; from there on, this function will return the current
running event loop if present else it will return the
loop set by <a class="reference internal" href="#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>.</p>
</div>
</dd></dl>
<dl class="py function">
<dt class="sig sig-object py" id="asyncio.set_event_loop">
<span class="sig-prename descclassname"><span class="pre">asyncio.</span></span><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.set_event_loop" title="Link to this definition">¶</a></dt>
<dd><p>Set <em>loop</em> as the current event loop for the current OS thread.</p>
</dd></dl>
<dl class="py function">
<dt class="sig sig-object py" id="asyncio.new_event_loop">
<span class="sig-prename descclassname"><span class="pre">asyncio.</span></span><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.new_event_loop" title="Link to this definition">¶</a></dt>
<dd><p>Create and return a new event loop object.</p>
</dd></dl>
<p>Note that the behaviour of <a class="reference internal" href="#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.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.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> functions can be altered by
<a class="reference internal" href="asyncio-policy.html#asyncio-policies"><span class="std std-ref">setting a custom event loop policy</span></a>.</p>
<p class="rubric">Contents</p>
<p>This documentation page contains the following sections:</p>
<ul class="simple">
<li><p>The <a class="reference internal" href="#event-loop-methods">Event Loop Methods</a> section is the reference documentation of
the event loop APIs;</p></li>
<li><p>The <a class="reference internal" href="#callback-handles">Callback Handles</a> section documents the <a class="reference internal" href="#asyncio.Handle" title="asyncio.Handle"><code class="xref py py-class docutils literal notranslate"><span class="pre">Handle</span></code></a> and
<a class="reference internal" href="#asyncio.TimerHandle" title="asyncio.TimerHandle"><code class="xref py py-class docutils literal notranslate"><span class="pre">TimerHandle</span></code></a> instances which are returned from scheduling
methods such as <a class="reference internal" href="#asyncio.loop.call_soon" title="asyncio.loop.call_soon"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.call_soon()</span></code></a> and <a class="reference internal" href="#asyncio.loop.call_later" title="asyncio.loop.call_later"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.call_later()</span></code></a>;</p></li>
<li><p>The <a class="reference internal" href="#server-objects">Server Objects</a> section documents types returned from
event loop methods like <a class="reference internal" href="#asyncio.loop.create_server" title="asyncio.loop.create_server"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_server()</span></code></a>;</p></li>
<li><p>The <a class="reference internal" href="#event-loop-implementations">Event Loop Implementations</a> section documents the
<a class="reference internal" href="#asyncio.SelectorEventLoop" title="asyncio.SelectorEventLoop"><code class="xref py py-class docutils literal notranslate"><span class="pre">SelectorEventLoop</span></code></a> and <a class="reference internal" href="#asyncio.ProactorEventLoop" title="asyncio.ProactorEventLoop"><code class="xref py py-class docutils literal notranslate"><span class="pre">ProactorEventLoop</span></code></a> classes;</p></li>
<li><p>The <a class="reference internal" href="#examples">Examples</a> section showcases how to work with some event
loop APIs.</p></li>
</ul>
<section id="event-loop-methods">
<span id="asyncio-event-loop-methods"></span><h2>Event Loop Methods<a class="headerlink" href="#event-loop-methods" title="Link to this heading">¶</a></h2>
<p>Event loops have <strong>low-level</strong> APIs for the following:</p>
<nav class="contents local" id="contents">
<ul class="simple">
<li><p><a class="reference internal" href="#running-and-stopping-the-loop" id="id1">Running and stopping the loop</a></p></li>
<li><p><a class="reference internal" href="#scheduling-callbacks" id="id2">Scheduling callbacks</a></p></li>
<li><p><a class="reference internal" href="#scheduling-delayed-callbacks" id="id3">Scheduling delayed callbacks</a></p></li>
<li><p><a class="reference internal" href="#creating-futures-and-tasks" id="id4">Creating Futures and Tasks</a></p></li>
<li><p><a class="reference internal" href="#opening-network-connections" id="id5">Opening network connections</a></p></li>
<li><p><a class="reference internal" href="#creating-network-servers" id="id6">Creating network servers</a></p></li>
<li><p><a class="reference internal" href="#transferring-files" id="id7">Transferring files</a></p></li>
<li><p><a class="reference internal" href="#tls-upgrade" id="id8">TLS Upgrade</a></p></li>
<li><p><a class="reference internal" href="#watching-file-descriptors" id="id9">Watching file descriptors</a></p></li>
<li><p><a class="reference internal" href="#working-with-socket-objects-directly" id="id10">Working with socket objects directly</a></p></li>
<li><p><a class="reference internal" href="#dns" id="id11">DNS</a></p></li>
<li><p><a class="reference internal" href="#working-with-pipes" id="id12">Working with pipes</a></p></li>
<li><p><a class="reference internal" href="#unix-signals" id="id13">Unix signals</a></p></li>
<li><p><a class="reference internal" href="#executing-code-in-thread-or-process-pools" id="id14">Executing code in thread or process pools</a></p></li>
<li><p><a class="reference internal" href="#error-handling-api" id="id15">Error Handling API</a></p></li>
<li><p><a class="reference internal" href="#enabling-debug-mode" id="id16">Enabling debug mode</a></p></li>
<li><p><a class="reference internal" href="#running-subprocesses" id="id17">Running Subprocesses</a></p></li>
</ul>
</nav>
<section id="running-and-stopping-the-loop">
<h3><a class="toc-backref" href="#id1" role="doc-backlink">Running and stopping the loop</a><a class="headerlink" href="#running-and-stopping-the-loop" title="Link to this heading">¶</a></h3>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.run_until_complete">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">run_until_complete</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">future</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.run_until_complete" title="Link to this definition">¶</a></dt>
<dd><p>Run until the <em>future</em> (an instance of <a class="reference internal" href="asyncio-future.html#asyncio.Future" title="asyncio.Future"><code class="xref py py-class docutils literal notranslate"><span class="pre">Future</span></code></a>) has
completed.</p>
<p>If the argument is a <a class="reference internal" href="asyncio-task.html#coroutine"><span class="std std-ref">coroutine object</span></a> it
is implicitly scheduled to run as a <a class="reference internal" href="asyncio-task.html#asyncio.Task" title="asyncio.Task"><code class="xref py py-class docutils literal notranslate"><span class="pre">asyncio.Task</span></code></a>.</p>
<p>Return the Future’s result or raise its exception.</p>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.run_forever">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">run_forever</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.run_forever" title="Link to this definition">¶</a></dt>
<dd><p>Run the event loop until <a class="reference internal" href="#asyncio.loop.stop" title="asyncio.loop.stop"><code class="xref py py-meth docutils literal notranslate"><span class="pre">stop()</span></code></a> is called.</p>
<p>If <a class="reference internal" href="#asyncio.loop.stop" title="asyncio.loop.stop"><code class="xref py py-meth docutils literal notranslate"><span class="pre">stop()</span></code></a> is called before <code class="xref py py-meth docutils literal notranslate"><span class="pre">run_forever()</span></code> is called,
the loop will poll the I/O selector once with a timeout of zero,
run all callbacks scheduled in response to I/O events (and
those that were already scheduled), and then exit.</p>
<p>If <a class="reference internal" href="#asyncio.loop.stop" title="asyncio.loop.stop"><code class="xref py py-meth docutils literal notranslate"><span class="pre">stop()</span></code></a> is called while <code class="xref py py-meth docutils literal notranslate"><span class="pre">run_forever()</span></code> is running,
the loop will run the current batch of callbacks and then exit.
Note that new callbacks scheduled by callbacks will not run in this
case; instead, they will run the next time <code class="xref py py-meth docutils literal notranslate"><span class="pre">run_forever()</span></code> or
<a class="reference internal" href="#asyncio.loop.run_until_complete" title="asyncio.loop.run_until_complete"><code class="xref py py-meth docutils literal notranslate"><span class="pre">run_until_complete()</span></code></a> is called.</p>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.stop">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">stop</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.stop" title="Link to this definition">¶</a></dt>
<dd><p>Stop the event loop.</p>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.is_running">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">is_running</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.is_running" title="Link to this definition">¶</a></dt>
<dd><p>Return <code class="docutils literal notranslate"><span class="pre">True</span></code> if the event loop is currently running.</p>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.is_closed">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">is_closed</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.is_closed" title="Link to this definition">¶</a></dt>
<dd><p>Return <code class="docutils literal notranslate"><span class="pre">True</span></code> if the event loop was closed.</p>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.close">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">close</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.close" title="Link to this definition">¶</a></dt>
<dd><p>Close the event loop.</p>
<p>The loop must not be running when this function is called.
Any pending callbacks will be discarded.</p>
<p>This method clears all queues and shuts down the executor, but does
not wait for the executor to finish.</p>
<p>This method is idempotent and irreversible. No other methods
should be called after the event loop is closed.</p>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.shutdown_asyncgens">
<em class="property"><span class="k"><span class="pre">async</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">shutdown_asyncgens</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.shutdown_asyncgens" title="Link to this definition">¶</a></dt>
<dd><p>Schedule all currently open <a class="reference internal" href="../glossary.html#term-asynchronous-generator"><span class="xref std std-term">asynchronous generator</span></a> objects to
close with an <a class="reference internal" href="../reference/expressions.html#agen.aclose" title="agen.aclose"><code class="xref py py-meth docutils literal notranslate"><span class="pre">aclose()</span></code></a> call. After calling this method,
the event loop will issue a warning if a new asynchronous generator
is iterated. This should be used to reliably finalize all scheduled
asynchronous generators.</p>
<p>Note that there is no need to call this function when
<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> is used.</p>
<p>Example:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">try</span><span class="p">:</span>
<span class="n">loop</span><span class="o">.</span><span class="n">run_forever</span><span class="p">()</span>
<span class="k">finally</span><span class="p">:</span>
<span class="n">loop</span><span class="o">.</span><span class="n">run_until_complete</span><span class="p">(</span><span class="n">loop</span><span class="o">.</span><span class="n">shutdown_asyncgens</span><span class="p">())</span>
<span class="n">loop</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
</pre></div>
</div>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.6.</span></p>
</div>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.shutdown_default_executor">
<em class="property"><span class="k"><span class="pre">async</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">shutdown_default_executor</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">timeout</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.shutdown_default_executor" title="Link to this definition">¶</a></dt>
<dd><p>Schedule the closure of the default executor and wait for it to join all of
the threads in the <a class="reference internal" href="concurrent.futures.html#concurrent.futures.ThreadPoolExecutor" title="concurrent.futures.ThreadPoolExecutor"><code class="xref py py-class docutils literal notranslate"><span class="pre">ThreadPoolExecutor</span></code></a>.
Once this method has been called,
using the default executor with <a class="reference internal" href="#asyncio.loop.run_in_executor" title="asyncio.loop.run_in_executor"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.run_in_executor()</span></code></a>
will raise 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>.</p>
<p>The <em>timeout</em> parameter specifies the amount of time
(in <a class="reference internal" href="functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate"><span class="pre">float</span></code></a> seconds) the executor will be given to finish joining.
With the default, <code class="docutils literal notranslate"><span class="pre">None</span></code>,
the executor is allowed an unlimited amount of time.</p>
<p>If the <em>timeout</em> is reached, a <a class="reference internal" href="exceptions.html#RuntimeWarning" title="RuntimeWarning"><code class="xref py py-exc docutils literal notranslate"><span class="pre">RuntimeWarning</span></code></a> is emitted
and the default executor is terminated
without waiting for its threads to finish joining.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>Do not call this method when using <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>,
as the latter handles default executor shutdown automatically.</p>
</div>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.9.</span></p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.12: </span>Added the <em>timeout</em> parameter.</p>
</div>
</dd></dl>
</section>
<section id="scheduling-callbacks">
<h3><a class="toc-backref" href="#id2" role="doc-backlink">Scheduling callbacks</a><a class="headerlink" href="#scheduling-callbacks" title="Link to this heading">¶</a></h3>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.call_soon">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">call_soon</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">callback</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">*</span></span><span class="n"><span class="pre">args</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">context</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.call_soon" title="Link to this definition">¶</a></dt>
<dd><p>Schedule the <em>callback</em> <a class="reference internal" href="../glossary.html#term-callback"><span class="xref std std-term">callback</span></a> to be called with
<em>args</em> arguments at the next iteration of the event loop.</p>
<p>Return an instance of <a class="reference internal" href="#asyncio.Handle" title="asyncio.Handle"><code class="xref py py-class docutils literal notranslate"><span class="pre">asyncio.Handle</span></code></a>,
which can be used later to cancel the callback.</p>
<p>Callbacks are called in the order in which they are registered.
Each callback will be called exactly once.</p>
<p>The optional keyword-only <em>context</em> argument specifies a
custom <a class="reference internal" href="contextvars.html#contextvars.Context" title="contextvars.Context"><code class="xref py py-class docutils literal notranslate"><span class="pre">contextvars.Context</span></code></a> for the <em>callback</em> to run in.
Callbacks use the current context when no <em>context</em> is provided.</p>
<p>Unlike <a class="reference internal" href="#asyncio.loop.call_soon_threadsafe" title="asyncio.loop.call_soon_threadsafe"><code class="xref py py-meth docutils literal notranslate"><span class="pre">call_soon_threadsafe()</span></code></a>, this method is not thread-safe.</p>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.call_soon_threadsafe">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">call_soon_threadsafe</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">callback</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">*</span></span><span class="n"><span class="pre">args</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">context</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.call_soon_threadsafe" title="Link to this definition">¶</a></dt>
<dd><p>A thread-safe variant of <a class="reference internal" href="#asyncio.loop.call_soon" title="asyncio.loop.call_soon"><code class="xref py py-meth docutils literal notranslate"><span class="pre">call_soon()</span></code></a>. When scheduling callbacks from
another thread, this function <em>must</em> be used, since <code class="xref py py-meth docutils literal notranslate"><span class="pre">call_soon()</span></code> is not
thread-safe.</p>
<p>This function is safe to be called from a reentrant context or signal handler,
however, it is not safe or fruitful to use the returned handle in such contexts.</p>
<p>Raises <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 called on a loop that’s been closed.
This can happen on a secondary thread when the main application is
shutting down.</p>
<p>See the <a class="reference internal" href="asyncio-dev.html#asyncio-multithreading"><span class="std std-ref">concurrency and multithreading</span></a>
section of the documentation.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.7: </span>The <em>context</em> keyword-only parameter was added. See <span class="target" id="index-0"></span><a class="pep reference external" href="https://peps.python.org/pep-0567/"><strong>PEP 567</strong></a>
for more details.</p>
</div>
</dd></dl>
<div class="admonition note" id="asyncio-pass-keywords">
<p class="admonition-title">Note</p>
<p>Most <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> scheduling functions don’t allow passing
keyword arguments. To do that, use <a class="reference internal" href="functools.html#functools.partial" title="functools.partial"><code class="xref py py-func docutils literal notranslate"><span class="pre">functools.partial()</span></code></a>:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="c1"># will schedule "print("Hello", flush=True)"</span>
<span class="n">loop</span><span class="o">.</span><span class="n">call_soon</span><span class="p">(</span>
<span class="n">functools</span><span class="o">.</span><span class="n">partial</span><span class="p">(</span><span class="nb">print</span><span class="p">,</span> <span class="s2">"Hello"</span><span class="p">,</span> <span class="n">flush</span><span class="o">=</span><span class="kc">True</span><span class="p">))</span>
</pre></div>
</div>
<p>Using partial objects is usually more convenient than using lambdas,
as asyncio can render partial objects better in debug and error
messages.</p>
</div>
</section>
<section id="scheduling-delayed-callbacks">
<span id="asyncio-delayed-calls"></span><h3><a class="toc-backref" href="#id3" role="doc-backlink">Scheduling delayed callbacks</a><a class="headerlink" href="#scheduling-delayed-callbacks" title="Link to this heading">¶</a></h3>
<p>Event loop provides mechanisms to schedule callback functions
to be called at some point in the future. Event loop uses monotonic
clocks to track time.</p>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.call_later">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">call_later</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">delay</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">callback</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">*</span></span><span class="n"><span class="pre">args</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">context</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.call_later" title="Link to this definition">¶</a></dt>
<dd><p>Schedule <em>callback</em> to be called after the given <em>delay</em>
number of seconds (can be either an int or a float).</p>
<p>An instance of <a class="reference internal" href="#asyncio.TimerHandle" title="asyncio.TimerHandle"><code class="xref py py-class docutils literal notranslate"><span class="pre">asyncio.TimerHandle</span></code></a> is returned which can
be used to cancel the callback.</p>
<p><em>callback</em> will be called exactly once. If two callbacks are
scheduled for exactly the same time, the order in which they
are called is undefined.</p>
<p>The optional positional <em>args</em> will be passed to the callback when
it is called. Use <a class="reference internal" href="functools.html#functools.partial" title="functools.partial"><code class="xref py py-func docutils literal notranslate"><span class="pre">functools.partial()</span></code></a>
<a class="reference internal" href="#asyncio-pass-keywords"><span class="std std-ref">to pass keyword arguments</span></a> to
<em>callback</em>.</p>
<p>An optional keyword-only <em>context</em> argument allows specifying a
custom <a class="reference internal" href="contextvars.html#contextvars.Context" title="contextvars.Context"><code class="xref py py-class docutils literal notranslate"><span class="pre">contextvars.Context</span></code></a> for the <em>callback</em> to run in.
The current context is used when no <em>context</em> is provided.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>For performance, callbacks scheduled with <code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.call_later()</span></code>
may run up to one clock-resolution early (see
<code class="docutils literal notranslate"><span class="pre">time.get_clock_info('monotonic').resolution</span></code>).</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.7: </span>The <em>context</em> keyword-only parameter was added. See <span class="target" id="index-1"></span><a class="pep reference external" href="https://peps.python.org/pep-0567/"><strong>PEP 567</strong></a>
for more details.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.8: </span>In Python 3.7 and earlier with the default event loop implementation,
the <em>delay</em> could not exceed one day.
This has been fixed in Python 3.8.</p>
</div>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.call_at">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">call_at</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">when</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">callback</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">*</span></span><span class="n"><span class="pre">args</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">context</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.call_at" title="Link to this definition">¶</a></dt>
<dd><p>Schedule <em>callback</em> to be called at the given absolute timestamp
<em>when</em> (an int or a float), using the same time reference as
<a class="reference internal" href="#asyncio.loop.time" title="asyncio.loop.time"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.time()</span></code></a>.</p>
<p>This method’s behavior is the same as <a class="reference internal" href="#asyncio.loop.call_later" title="asyncio.loop.call_later"><code class="xref py py-meth docutils literal notranslate"><span class="pre">call_later()</span></code></a>.</p>
<p>An instance of <a class="reference internal" href="#asyncio.TimerHandle" title="asyncio.TimerHandle"><code class="xref py py-class docutils literal notranslate"><span class="pre">asyncio.TimerHandle</span></code></a> is returned which can
be used to cancel the callback.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>For performance, callbacks scheduled with <code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.call_at()</span></code>
may run up to one clock-resolution early (see
<code class="docutils literal notranslate"><span class="pre">time.get_clock_info('monotonic').resolution</span></code>).</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.7: </span>The <em>context</em> keyword-only parameter was added. See <span class="target" id="index-2"></span><a class="pep reference external" href="https://peps.python.org/pep-0567/"><strong>PEP 567</strong></a>
for more details.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.8: </span>In Python 3.7 and earlier with the default event loop implementation,
the difference between <em>when</em> and the current time could not exceed
one day. This has been fixed in Python 3.8.</p>
</div>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.time">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">time</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.time" title="Link to this definition">¶</a></dt>
<dd><p>Return the current time, as a <a class="reference internal" href="functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate"><span class="pre">float</span></code></a> value, according to
the event loop’s internal monotonic clock.</p>
</dd></dl>
<div class="admonition note">
<p class="admonition-title">Note</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.8: </span>In Python 3.7 and earlier timeouts (relative <em>delay</em> or absolute <em>when</em>)
should not exceed one day. This has been fixed in Python 3.8.</p>
</div>
</div>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<p>The <a class="reference internal" href="asyncio-task.html#asyncio.sleep" title="asyncio.sleep"><code class="xref py py-func docutils literal notranslate"><span class="pre">asyncio.sleep()</span></code></a> function.</p>
</div>
</section>
<section id="creating-futures-and-tasks">
<h3><a class="toc-backref" href="#id4" role="doc-backlink">Creating Futures and Tasks</a><a class="headerlink" href="#creating-futures-and-tasks" title="Link to this heading">¶</a></h3>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.create_future">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">create_future</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.create_future" title="Link to this definition">¶</a></dt>
<dd><p>Create an <a class="reference internal" href="asyncio-future.html#asyncio.Future" title="asyncio.Future"><code class="xref py py-class docutils literal notranslate"><span class="pre">asyncio.Future</span></code></a> object attached to the event loop.</p>
<p>This is the preferred way to create Futures in asyncio. This lets
third-party event loops provide alternative implementations of
the Future object (with better performance or instrumentation).</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.5.2.</span></p>
</div>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.create_task">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">create_task</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">coro</span></span></em>, <em class="sig-param"><span class="keyword-only-separator o"><abbr title="Keyword-only parameters separator (PEP 3102)"><span class="pre">*</span></abbr></span></em>, <em class="sig-param"><span class="n"><span class="pre">name</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">context</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">eager_start</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">**</span></span><span class="n"><span class="pre">kwargs</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.create_task" title="Link to this definition">¶</a></dt>
<dd><p>Schedule the execution of <a class="reference internal" href="asyncio-task.html#coroutine"><span class="std std-ref">coroutine</span></a> <em>coro</em>.
Return a <a class="reference internal" href="asyncio-task.html#asyncio.Task" title="asyncio.Task"><code class="xref py py-class docutils literal notranslate"><span class="pre">Task</span></code></a> object.</p>
<p>Third-party event loops can use their own subclass of <a class="reference internal" href="asyncio-task.html#asyncio.Task" title="asyncio.Task"><code class="xref py py-class docutils literal notranslate"><span class="pre">Task</span></code></a>
for interoperability. In this case, the result type is a subclass
of <code class="xref py py-class docutils literal notranslate"><span class="pre">Task</span></code>.</p>
<p>The full function signature is largely the same as that of the
<a class="reference internal" href="asyncio-task.html#asyncio.Task" title="asyncio.Task"><code class="xref py py-class docutils literal notranslate"><span class="pre">Task</span></code></a> constructor (or factory) - all of the keyword arguments to
this function are passed through to that interface.</p>
<p>If the <em>name</em> argument is provided and not <code class="docutils literal notranslate"><span class="pre">None</span></code>, it is set as
the name of the task using <a class="reference internal" href="asyncio-task.html#asyncio.Task.set_name" title="asyncio.Task.set_name"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Task.set_name()</span></code></a>.</p>
<p>An optional keyword-only <em>context</em> argument allows specifying a
custom <a class="reference internal" href="contextvars.html#contextvars.Context" title="contextvars.Context"><code class="xref py py-class docutils literal notranslate"><span class="pre">contextvars.Context</span></code></a> for the <em>coro</em> to run in.
The current context copy is created when no <em>context</em> is provided.</p>
<p>An optional keyword-only <em>eager_start</em> argument allows specifying
if the task should execute eagerly during the call to create_task,
or be scheduled later. If <em>eager_start</em> is not passed the mode set
by <a class="reference internal" href="#asyncio.loop.set_task_factory" title="asyncio.loop.set_task_factory"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.set_task_factory()</span></code></a> will be used.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.8: </span>Added the <em>name</em> parameter.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.11: </span>Added the <em>context</em> parameter.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.13.3: </span>Added <code class="docutils literal notranslate"><span class="pre">kwargs</span></code> which passes on arbitrary extra parameters, including <code class="docutils literal notranslate"><span class="pre">name</span></code> and <code class="docutils literal notranslate"><span class="pre">context</span></code>.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.13.4: </span>Rolled back the change that passes on <em>name</em> and <em>context</em> (if it is None),
while still passing on other arbitrary keyword arguments (to avoid breaking backwards compatibility with 3.13.3).</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.14: </span>All <em>kwargs</em> are now passed on. The <em>eager_start</em> parameter works with eager task factories.</p>
</div>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.set_task_factory">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">set_task_factory</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">factory</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.set_task_factory" title="Link to this definition">¶</a></dt>
<dd><p>Set a task factory that will be used by
<a class="reference internal" href="#asyncio.loop.create_task" title="asyncio.loop.create_task"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_task()</span></code></a>.</p>
<p>If <em>factory</em> is <code class="docutils literal notranslate"><span class="pre">None</span></code> the default task factory will be set.
Otherwise, <em>factory</em> must be a <em>callable</em> with the signature matching
<code class="docutils literal notranslate"><span class="pre">(loop,</span> <span class="pre">coro,</span> <span class="pre">**kwargs)</span></code>, where <em>loop</em> is a reference to the active
event loop, and <em>coro</em> is a coroutine object. The callable
must pass on all <em>kwargs</em>, and return a <a class="reference internal" href="asyncio-task.html#asyncio.Task" title="asyncio.Task"><code class="xref py py-class docutils literal notranslate"><span class="pre">asyncio.Task</span></code></a>-compatible object.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.13.3: </span>Required that all <em>kwargs</em> are passed on to <a class="reference internal" href="asyncio-task.html#asyncio.Task" title="asyncio.Task"><code class="xref py py-class docutils literal notranslate"><span class="pre">asyncio.Task</span></code></a>.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.13.4: </span><em>name</em> is no longer passed to task factories. <em>context</em> is no longer passed
to task factories if it is <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.14: </span><em>name</em> and <em>context</em> are now unconditionally passed on to task factories again.</p>
</div>
</div>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.get_task_factory">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">get_task_factory</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.get_task_factory" title="Link to this definition">¶</a></dt>
<dd><p>Return a task factory or <code class="docutils literal notranslate"><span class="pre">None</span></code> if the default one is in use.</p>
</dd></dl>
</section>
<section id="opening-network-connections">
<h3><a class="toc-backref" href="#id5" role="doc-backlink">Opening network connections</a><a class="headerlink" href="#opening-network-connections" title="Link to this heading">¶</a></h3>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.create_connection">
<em class="property"><span class="k"><span class="pre">async</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">create_connection</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">protocol_factory</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">host</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">port</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="keyword-only-separator o"><abbr title="Keyword-only parameters separator (PEP 3102)"><span class="pre">*</span></abbr></span></em>, <em class="sig-param"><span class="n"><span class="pre">ssl</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">family</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">0</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">proto</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">0</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">flags</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">0</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">sock</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">local_addr</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">server_hostname</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">ssl_handshake_timeout</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">ssl_shutdown_timeout</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">happy_eyeballs_delay</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">interleave</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">all_errors</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">False</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.create_connection" title="Link to this definition">¶</a></dt>
<dd><p>Open a streaming transport connection to a given
address specified by <em>host</em> and <em>port</em>.</p>
<p>The socket family can be either <a class="reference internal" href="socket.html#socket.AF_INET" title="socket.AF_INET"><code class="xref py py-const docutils literal notranslate"><span class="pre">AF_INET</span></code></a> or
<a class="reference internal" href="socket.html#socket.AF_INET6" title="socket.AF_INET6"><code class="xref py py-const docutils literal notranslate"><span class="pre">AF_INET6</span></code></a> depending on <em>host</em> (or the <em>family</em>
argument, if provided).</p>
<p>The socket type will be <a class="reference internal" href="socket.html#socket.SOCK_STREAM" title="socket.SOCK_STREAM"><code class="xref py py-const docutils literal notranslate"><span class="pre">SOCK_STREAM</span></code></a>.</p>
<p><em>protocol_factory</em> must be a callable returning an
<a class="reference internal" href="asyncio-protocol.html#asyncio-protocol"><span class="std std-ref">asyncio protocol</span></a> implementation.</p>
<p>This method will try to establish the connection in the background.
When successful, it returns a <code class="docutils literal notranslate"><span class="pre">(transport,</span> <span class="pre">protocol)</span></code> pair.</p>
<p>The chronological synopsis of the underlying operation is as follows:</p>
<ol class="arabic simple">
<li><p>The connection is established and a <a class="reference internal" href="asyncio-protocol.html#asyncio-transport"><span class="std std-ref">transport</span></a>
is created for it.</p></li>
<li><p><em>protocol_factory</em> is called without arguments and is expected to
return a <a class="reference internal" href="asyncio-protocol.html#asyncio-protocol"><span class="std std-ref">protocol</span></a> instance.</p></li>
<li><p>The protocol instance is coupled with the transport by calling its
<a class="reference internal" href="asyncio-protocol.html#asyncio.BaseProtocol.connection_made" title="asyncio.BaseProtocol.connection_made"><code class="xref py py-meth docutils literal notranslate"><span class="pre">connection_made()</span></code></a> method.</p></li>
<li><p>A <code class="docutils literal notranslate"><span class="pre">(transport,</span> <span class="pre">protocol)</span></code> tuple is returned on success.</p></li>
</ol>
<p>The created transport is an implementation-dependent bidirectional
stream.</p>
<p>Other arguments:</p>
<ul>
<li><p><em>ssl</em>: if given and not false, a SSL/TLS transport is created
(by default a plain TCP transport is created). If <em>ssl</em> is
a <a class="reference internal" href="ssl.html#ssl.SSLContext" title="ssl.SSLContext"><code class="xref py py-class docutils literal notranslate"><span class="pre">ssl.SSLContext</span></code></a> object, this context is used to create
the transport; if <em>ssl</em> is <a class="reference internal" href="constants.html#True" title="True"><code class="xref py py-const docutils literal notranslate"><span class="pre">True</span></code></a>, a default context returned
from <a class="reference internal" href="ssl.html#ssl.create_default_context" title="ssl.create_default_context"><code class="xref py py-func docutils literal notranslate"><span class="pre">ssl.create_default_context()</span></code></a> is used.</p>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<p><a class="reference internal" href="ssl.html#ssl-security"><span class="std std-ref">SSL/TLS security considerations</span></a></p>
</div>
</li>
<li><p><em>server_hostname</em> sets or overrides the hostname that the target
server’s certificate will be matched against. Should only be passed
if <em>ssl</em> is not <code class="docutils literal notranslate"><span class="pre">None</span></code>. By default the value of the <em>host</em> argument
is used. If <em>host</em> is empty, there is no default and you must pass a
value for <em>server_hostname</em>. If <em>server_hostname</em> is an empty
string, hostname matching is disabled (which is a serious security
risk, allowing for potential man-in-the-middle attacks).</p></li>
<li><p><em>family</em>, <em>proto</em>, <em>flags</em> are the optional address family, protocol
and flags to be passed through to getaddrinfo() for <em>host</em> resolution.
If given, these should all be integers from the corresponding
<a class="reference internal" href="socket.html#module-socket" title="socket: Low-level networking interface."><code class="xref py py-mod docutils literal notranslate"><span class="pre">socket</span></code></a> module constants.</p></li>
<li><p><em>happy_eyeballs_delay</em>, if given, enables Happy Eyeballs for this
connection. It should
be a floating-point number representing the amount of time in seconds
to wait for a connection attempt to complete, before starting the next
attempt in parallel. This is the “Connection Attempt Delay” as defined
in <span class="target" id="index-3"></span><a class="rfc reference external" href="https://datatracker.ietf.org/doc/html/rfc8305.html"><strong>RFC 8305</strong></a>. A sensible default value recommended by the RFC is <code class="docutils literal notranslate"><span class="pre">0.25</span></code>
(250 milliseconds).</p></li>
<li><p><em>interleave</em> controls address reordering when a host name resolves to
multiple IP addresses.
If <code class="docutils literal notranslate"><span class="pre">0</span></code> or unspecified, no reordering is done, and addresses are
tried in the order returned by <a class="reference internal" href="#asyncio.loop.getaddrinfo" title="asyncio.loop.getaddrinfo"><code class="xref py py-meth docutils literal notranslate"><span class="pre">getaddrinfo()</span></code></a>. If a positive integer
is specified, the addresses are interleaved by address family, and the
given integer is interpreted as “First Address Family Count” as defined
in <span class="target" id="index-4"></span><a class="rfc reference external" href="https://datatracker.ietf.org/doc/html/rfc8305.html"><strong>RFC 8305</strong></a>. The default is <code class="docutils literal notranslate"><span class="pre">0</span></code> if <em>happy_eyeballs_delay</em> is not
specified, and <code class="docutils literal notranslate"><span class="pre">1</span></code> if it is.</p></li>
<li><p><em>sock</em>, if given, should be an existing, already connected
<a class="reference internal" href="socket.html#socket.socket" title="socket.socket"><code class="xref py py-class docutils literal notranslate"><span class="pre">socket.socket</span></code></a> object to be used by the transport.
If <em>sock</em> is given, none of <em>host</em>, <em>port</em>, <em>family</em>, <em>proto</em>, <em>flags</em>,
<em>happy_eyeballs_delay</em>, <em>interleave</em>
and <em>local_addr</em> should be specified.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>The <em>sock</em> argument transfers ownership of the socket to the
transport created. To close the socket, call the transport’s
<a class="reference internal" href="asyncio-protocol.html#asyncio.BaseTransport.close" title="asyncio.BaseTransport.close"><code class="xref py py-meth docutils literal notranslate"><span class="pre">close()</span></code></a> method.</p>
</div>
</li>
<li><p><em>local_addr</em>, if given, is a <code class="docutils literal notranslate"><span class="pre">(local_host,</span> <span class="pre">local_port)</span></code> tuple used
to bind the socket locally. The <em>local_host</em> and <em>local_port</em>
are looked up using <code class="docutils literal notranslate"><span class="pre">getaddrinfo()</span></code>, similarly to <em>host</em> and <em>port</em>.</p></li>
<li><p><em>ssl_handshake_timeout</em> is (for a TLS connection) the time in seconds
to wait for the TLS handshake to complete before aborting the connection.
<code class="docutils literal notranslate"><span class="pre">60.0</span></code> seconds if <code class="docutils literal notranslate"><span class="pre">None</span></code> (default).</p></li>
<li><p><em>ssl_shutdown_timeout</em> is the time in seconds to wait for the SSL shutdown
to complete before aborting the connection. <code class="docutils literal notranslate"><span class="pre">30.0</span></code> seconds if <code class="docutils literal notranslate"><span class="pre">None</span></code>
(default).</p></li>
<li><p><em>all_errors</em> determines what exceptions are raised when a connection cannot
be created. By default, only a single <code class="docutils literal notranslate"><span class="pre">Exception</span></code> is raised: the first
exception if there is only one or all errors have same message, or a single
<code class="docutils literal notranslate"><span class="pre">OSError</span></code> with the error messages combined. When <code class="docutils literal notranslate"><span class="pre">all_errors</span></code> is <code class="docutils literal notranslate"><span class="pre">True</span></code>,
an <code class="docutils literal notranslate"><span class="pre">ExceptionGroup</span></code> will be raised containing all exceptions (even if there
is only one).</p></li>
</ul>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.5: </span>Added support for SSL/TLS in <a class="reference internal" href="#asyncio.ProactorEventLoop" title="asyncio.ProactorEventLoop"><code class="xref py py-class docutils literal notranslate"><span class="pre">ProactorEventLoop</span></code></a>.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.6: </span>The socket option <a class="reference internal" href="socket.html#socket-unix-constants"><span class="std std-ref">socket.TCP_NODELAY</span></a> is set by default
for all TCP connections.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.7: </span>Added the <em>ssl_handshake_timeout</em> parameter.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.8: </span>Added the <em>happy_eyeballs_delay</em> and <em>interleave</em> parameters.</p>
<p>Happy Eyeballs Algorithm: Success with Dual-Stack Hosts.
When a server’s IPv4 path and protocol are working, but the server’s
IPv6 path and protocol are not working, a dual-stack client
application experiences significant connection delay compared to an
IPv4-only client. This is undesirable because it causes the
dual-stack client to have a worse user experience. This document
specifies requirements for algorithms that reduce this user-visible
delay and provides an algorithm.</p>
<p>For more information: <a class="reference external" href="https://datatracker.ietf.org/doc/html/rfc6555">https://datatracker.ietf.org/doc/html/rfc6555</a></p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.11: </span>Added the <em>ssl_shutdown_timeout</em> parameter.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.12: </span><em>all_errors</em> was added.</p>
</div>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<p>The <a class="reference internal" href="asyncio-stream.html#asyncio.open_connection" title="asyncio.open_connection"><code class="xref py py-func docutils literal notranslate"><span class="pre">open_connection()</span></code></a> function is a high-level alternative
API. It returns a pair of (<a class="reference internal" href="asyncio-stream.html#asyncio.StreamReader" title="asyncio.StreamReader"><code class="xref py py-class docutils literal notranslate"><span class="pre">StreamReader</span></code></a>, <a class="reference internal" href="asyncio-stream.html#asyncio.StreamWriter" title="asyncio.StreamWriter"><code class="xref py py-class docutils literal notranslate"><span class="pre">StreamWriter</span></code></a>)
that can be used directly in async/await code.</p>
</div>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.create_datagram_endpoint">
<em class="property"><span class="k"><span class="pre">async</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">create_datagram_endpoint</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">protocol_factory</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">local_addr</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">remote_addr</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="keyword-only-separator o"><abbr title="Keyword-only parameters separator (PEP 3102)"><span class="pre">*</span></abbr></span></em>, <em class="sig-param"><span class="n"><span class="pre">family</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">0</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">proto</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">0</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">flags</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">0</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">reuse_port</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">allow_broadcast</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">sock</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.create_datagram_endpoint" title="Link to this definition">¶</a></dt>
<dd><p>Create a datagram connection.</p>
<p>The socket family can be either <a class="reference internal" href="socket.html#socket.AF_INET" title="socket.AF_INET"><code class="xref py py-const docutils literal notranslate"><span class="pre">AF_INET</span></code></a>,
<a class="reference internal" href="socket.html#socket.AF_INET6" title="socket.AF_INET6"><code class="xref py py-const docutils literal notranslate"><span class="pre">AF_INET6</span></code></a>, or <a class="reference internal" href="socket.html#socket.AF_UNIX" title="socket.AF_UNIX"><code class="xref py py-const docutils literal notranslate"><span class="pre">AF_UNIX</span></code></a>,
depending on <em>host</em> (or the <em>family</em> argument, if provided).</p>
<p>The socket type will be <a class="reference internal" href="socket.html#socket.SOCK_DGRAM" title="socket.SOCK_DGRAM"><code class="xref py py-const docutils literal notranslate"><span class="pre">SOCK_DGRAM</span></code></a>.</p>
<p><em>protocol_factory</em> must be a callable returning a
<a class="reference internal" href="asyncio-protocol.html#asyncio-protocol"><span class="std std-ref">protocol</span></a> implementation.</p>
<p>A tuple of <code class="docutils literal notranslate"><span class="pre">(transport,</span> <span class="pre">protocol)</span></code> is returned on success.</p>
<p>Other arguments:</p>
<ul>
<li><p><em>local_addr</em>, if given, is a <code class="docutils literal notranslate"><span class="pre">(local_host,</span> <span class="pre">local_port)</span></code> tuple used
to bind the socket locally. The <em>local_host</em> and <em>local_port</em>
are looked up using <a class="reference internal" href="#asyncio.loop.getaddrinfo" title="asyncio.loop.getaddrinfo"><code class="xref py py-meth docutils literal notranslate"><span class="pre">getaddrinfo()</span></code></a>.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>On Windows, when using the proactor event loop with <code class="docutils literal notranslate"><span class="pre">local_addr=None</span></code>,
an <a class="reference internal" href="exceptions.html#OSError" title="OSError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">OSError</span></code></a> with <code class="xref py py-attr docutils literal notranslate"><span class="pre">errno.WSAEINVAL</span></code> will be raised
when running it.</p>
</div>
</li>
<li><p><em>remote_addr</em>, if given, is a <code class="docutils literal notranslate"><span class="pre">(remote_host,</span> <span class="pre">remote_port)</span></code> tuple used
to connect the socket to a remote address. The <em>remote_host</em> and
<em>remote_port</em> are looked up using <a class="reference internal" href="#asyncio.loop.getaddrinfo" title="asyncio.loop.getaddrinfo"><code class="xref py py-meth docutils literal notranslate"><span class="pre">getaddrinfo()</span></code></a>.</p></li>
<li><p><em>family</em>, <em>proto</em>, <em>flags</em> are the optional address family, protocol
and flags to be passed through to <a class="reference internal" href="#asyncio.loop.getaddrinfo" title="asyncio.loop.getaddrinfo"><code class="xref py py-meth docutils literal notranslate"><span class="pre">getaddrinfo()</span></code></a> for <em>host</em>
resolution. If given, these should all be integers from the
corresponding <a class="reference internal" href="socket.html#module-socket" title="socket: Low-level networking interface."><code class="xref py py-mod docutils literal notranslate"><span class="pre">socket</span></code></a> module constants.</p></li>
<li><p><em>reuse_port</em> tells the kernel to allow this endpoint to be bound to the
same port as other existing endpoints are bound to, so long as they all
set this flag when being created. This option is not supported on Windows
and some Unixes. If the <a class="reference internal" href="socket.html#socket-unix-constants"><span class="std std-ref">socket.SO_REUSEPORT</span></a> constant is not
defined then this capability is unsupported.</p></li>
<li><p><em>allow_broadcast</em> tells the kernel to allow this endpoint to send
messages to the broadcast address.</p></li>
<li><p><em>sock</em> can optionally be specified in order to use a preexisting,
already connected, <a class="reference internal" href="socket.html#socket.socket" title="socket.socket"><code class="xref py py-class docutils literal notranslate"><span class="pre">socket.socket</span></code></a> object to be used by the
transport. If specified, <em>local_addr</em> and <em>remote_addr</em> should be omitted
(must be <a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal notranslate"><span class="pre">None</span></code></a>).</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>The <em>sock</em> argument transfers ownership of the socket to the
transport created. To close the socket, call the transport’s
<a class="reference internal" href="asyncio-protocol.html#asyncio.BaseTransport.close" title="asyncio.BaseTransport.close"><code class="xref py py-meth docutils literal notranslate"><span class="pre">close()</span></code></a> method.</p>
</div>
</li>
</ul>
<p>See <a class="reference internal" href="asyncio-protocol.html#asyncio-udp-echo-client-protocol"><span class="std std-ref">UDP echo client protocol</span></a> and
<a class="reference internal" href="asyncio-protocol.html#asyncio-udp-echo-server-protocol"><span class="std std-ref">UDP echo server protocol</span></a> examples.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.4.4: </span>The <em>family</em>, <em>proto</em>, <em>flags</em>, <em>reuse_address</em>, <em>reuse_port</em>,
<em>allow_broadcast</em>, and <em>sock</em> parameters were added.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.8: </span>Added support for Windows.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.8.1: </span>The <em>reuse_address</em> parameter is no longer supported, as using
<a class="reference internal" href="socket.html#socket-unix-constants"><span class="std std-ref">socket.SO_REUSEADDR</span></a>
poses a significant security concern for
UDP. Explicitly passing <code class="docutils literal notranslate"><span class="pre">reuse_address=True</span></code> will raise an exception.</p>
<p>When multiple processes with differing UIDs assign sockets to an
identical UDP socket address with <code class="docutils literal notranslate"><span class="pre">SO_REUSEADDR</span></code>, incoming packets can
become randomly distributed among the sockets.</p>
<p>For supported platforms, <em>reuse_port</em> can be used as a replacement for
similar functionality. With <em>reuse_port</em>,
<a class="reference internal" href="socket.html#socket-unix-constants"><span class="std std-ref">socket.SO_REUSEPORT</span></a>
is used instead, which specifically
prevents processes with differing UIDs from assigning sockets to the same
socket address.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.11: </span>The <em>reuse_address</em> parameter, disabled since Python 3.8.1,
3.7.6 and 3.6.10, has been entirely removed.</p>
</div>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.create_unix_connection">
<em class="property"><span class="k"><span class="pre">async</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">create_unix_connection</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">protocol_factory</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">path</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="keyword-only-separator o"><abbr title="Keyword-only parameters separator (PEP 3102)"><span class="pre">*</span></abbr></span></em>, <em class="sig-param"><span class="n"><span class="pre">ssl</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">sock</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">server_hostname</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">ssl_handshake_timeout</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">ssl_shutdown_timeout</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.create_unix_connection" title="Link to this definition">¶</a></dt>
<dd><p>Create a Unix connection.</p>
<p>The socket family will be <a class="reference internal" href="socket.html#socket.AF_UNIX" title="socket.AF_UNIX"><code class="xref py py-const docutils literal notranslate"><span class="pre">AF_UNIX</span></code></a>; socket
type will be <a class="reference internal" href="socket.html#socket.SOCK_STREAM" title="socket.SOCK_STREAM"><code class="xref py py-const docutils literal notranslate"><span class="pre">SOCK_STREAM</span></code></a>.</p>
<p>A tuple of <code class="docutils literal notranslate"><span class="pre">(transport,</span> <span class="pre">protocol)</span></code> is returned on success.</p>
<p><em>path</em> is the name of a Unix domain socket and is required,
unless a <em>sock</em> parameter is specified. Abstract Unix sockets,
<a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a>, <a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a>, and <a class="reference internal" href="pathlib.html#pathlib.Path" title="pathlib.Path"><code class="xref py py-class docutils literal notranslate"><span class="pre">Path</span></code></a> paths are
supported.</p>
<p>See the documentation of the <a class="reference internal" href="#asyncio.loop.create_connection" title="asyncio.loop.create_connection"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_connection()</span></code></a> method
for information about arguments to this method.</p>
<div class="availability docutils container">
<p><a class="reference internal" href="intro.html#availability"><span class="std std-ref">Availability</span></a>: Unix.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.7: </span>Added the <em>ssl_handshake_timeout</em> parameter.
The <em>path</em> parameter can now be a <a class="reference internal" href="../glossary.html#term-path-like-object"><span class="xref std std-term">path-like object</span></a>.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.11: </span>Added the <em>ssl_shutdown_timeout</em> parameter.</p>
</div>
</dd></dl>
</section>
<section id="creating-network-servers">
<h3><a class="toc-backref" href="#id6" role="doc-backlink">Creating network servers</a><a class="headerlink" href="#creating-network-servers" title="Link to this heading">¶</a></h3>
<dl class="py method" id="loop-create-server">
<dt class="sig sig-object py" id="asyncio.loop.create_server">
<em class="property"><span class="k"><span class="pre">async</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">create_server</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">protocol_factory</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">host</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">port</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="keyword-only-separator o"><abbr title="Keyword-only parameters separator (PEP 3102)"><span class="pre">*</span></abbr></span></em>, <em class="sig-param"><span class="n"><span class="pre">family</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">socket.AF_UNSPEC</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">flags</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">socket.AI_PASSIVE</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">sock</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">backlog</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">100</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">ssl</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">reuse_address</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">reuse_port</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">keep_alive</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">ssl_handshake_timeout</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">ssl_shutdown_timeout</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">start_serving</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">True</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.create_server" title="Link to this definition">¶</a></dt>
<dd><p>Create a TCP server (socket type <a class="reference internal" href="socket.html#socket.SOCK_STREAM" title="socket.SOCK_STREAM"><code class="xref py py-const docutils literal notranslate"><span class="pre">SOCK_STREAM</span></code></a>) listening
on <em>port</em> of the <em>host</em> address.</p>
<p>Returns a <a class="reference internal" href="#asyncio.Server" title="asyncio.Server"><code class="xref py py-class docutils literal notranslate"><span class="pre">Server</span></code></a> object.</p>
<p>Arguments:</p>
<ul>
<li><p><em>protocol_factory</em> must be a callable returning a
<a class="reference internal" href="asyncio-protocol.html#asyncio-protocol"><span class="std std-ref">protocol</span></a> implementation.</p></li>
<li><p>The <em>host</em> parameter can be set to several types which determine where
the server would be listening:</p>
<ul class="simple">
<li><p>If <em>host</em> is a string, the TCP server is bound to a single network
interface specified by <em>host</em>.</p></li>
<li><p>If <em>host</em> is a sequence of strings, the TCP server is bound to all
network interfaces specified by the sequence.</p></li>
<li><p>If <em>host</em> is an empty string or <code class="docutils literal notranslate"><span class="pre">None</span></code>, all interfaces are
assumed and a list of multiple sockets will be returned (most likely
one for IPv4 and another one for IPv6).</p></li>
</ul>
</li>
<li><p>The <em>port</em> parameter can be set to specify which port the server should
listen on. If <code class="docutils literal notranslate"><span class="pre">0</span></code> or <code class="docutils literal notranslate"><span class="pre">None</span></code> (the default), a random unused port will
be selected (note that if <em>host</em> resolves to multiple network interfaces,
a different random port will be selected for each interface).</p></li>
<li><p><em>family</em> can be set to either <a class="reference internal" href="socket.html#socket.AF_INET" title="socket.AF_INET"><code class="xref py py-const docutils literal notranslate"><span class="pre">socket.AF_INET</span></code></a> or
<a class="reference internal" href="socket.html#socket.AF_INET6" title="socket.AF_INET6"><code class="xref py py-const docutils literal notranslate"><span class="pre">AF_INET6</span></code></a> to force the socket to use IPv4 or IPv6.
If not set, the <em>family</em> will be determined from host name
(defaults to <a class="reference internal" href="socket.html#socket.AF_UNSPEC" title="socket.AF_UNSPEC"><code class="xref py py-const docutils literal notranslate"><span class="pre">AF_UNSPEC</span></code></a>).</p></li>
<li><p><em>flags</em> is a bitmask for <a class="reference internal" href="#asyncio.loop.getaddrinfo" title="asyncio.loop.getaddrinfo"><code class="xref py py-meth docutils literal notranslate"><span class="pre">getaddrinfo()</span></code></a>.</p></li>
<li><p><em>sock</em> can optionally be specified in order to use a preexisting
socket object. If specified, <em>host</em> and <em>port</em> must not be specified.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>The <em>sock</em> argument transfers ownership of the socket to the
server created. To close the socket, call the server’s
<a class="reference internal" href="#asyncio.Server.close" title="asyncio.Server.close"><code class="xref py py-meth docutils literal notranslate"><span class="pre">close()</span></code></a> method.</p>
</div>
</li>
<li><p><em>backlog</em> is the maximum number of queued connections passed to
<a class="reference internal" href="socket.html#socket.socket.listen" title="socket.socket.listen"><code class="xref py py-meth docutils literal notranslate"><span class="pre">listen()</span></code></a> (defaults to 100).</p></li>
<li><p><em>ssl</em> can be set to an <a class="reference internal" href="ssl.html#ssl.SSLContext" title="ssl.SSLContext"><code class="xref py py-class docutils literal notranslate"><span class="pre">SSLContext</span></code></a> instance to enable
TLS over the accepted connections.</p></li>
<li><p><em>reuse_address</em> tells the kernel to reuse a local socket in
<code class="docutils literal notranslate"><span class="pre">TIME_WAIT</span></code> state, without waiting for its natural timeout to
expire. If not specified will automatically be set to <code class="docutils literal notranslate"><span class="pre">True</span></code> on
Unix.</p></li>
<li><p><em>reuse_port</em> tells the kernel to allow this endpoint to be bound to the
same port as other existing endpoints are bound to, so long as they all
set this flag when being created. This option is not supported on
Windows.</p></li>
<li><p><em>keep_alive</em> set to <code class="docutils literal notranslate"><span class="pre">True</span></code> keeps connections active by enabling the
periodic transmission of messages.</p></li>
</ul>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.13: </span>Added the <em>keep_alive</em> parameter.</p>
</div>
<ul class="simple">
<li><p><em>ssl_handshake_timeout</em> is (for a TLS server) the time in seconds to wait
for the TLS handshake to complete before aborting the connection.
<code class="docutils literal notranslate"><span class="pre">60.0</span></code> seconds if <code class="docutils literal notranslate"><span class="pre">None</span></code> (default).</p></li>
<li><p><em>ssl_shutdown_timeout</em> is the time in seconds to wait for the SSL shutdown
to complete before aborting the connection. <code class="docutils literal notranslate"><span class="pre">30.0</span></code> seconds if <code class="docutils literal notranslate"><span class="pre">None</span></code>
(default).</p></li>
<li><p><em>start_serving</em> set to <code class="docutils literal notranslate"><span class="pre">True</span></code> (the default) causes the created server
to start accepting connections immediately. When set to <code class="docutils literal notranslate"><span class="pre">False</span></code>,
the user should await on <a class="reference internal" href="#asyncio.Server.start_serving" title="asyncio.Server.start_serving"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Server.start_serving()</span></code></a> or
<a class="reference internal" href="#asyncio.Server.serve_forever" title="asyncio.Server.serve_forever"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Server.serve_forever()</span></code></a> to make the server to start accepting
connections.</p></li>
</ul>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.5: </span>Added support for SSL/TLS in <a class="reference internal" href="#asyncio.ProactorEventLoop" title="asyncio.ProactorEventLoop"><code class="xref py py-class docutils literal notranslate"><span class="pre">ProactorEventLoop</span></code></a>.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.5.1: </span>The <em>host</em> parameter can be a sequence of strings.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.6: </span>Added <em>ssl_handshake_timeout</em> and <em>start_serving</em> parameters.
The socket option <a class="reference internal" href="socket.html#socket-unix-constants"><span class="std std-ref">socket.TCP_NODELAY</span></a> is set by default
for all TCP connections.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.11: </span>Added the <em>ssl_shutdown_timeout</em> parameter.</p>
</div>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<p>The <a class="reference internal" href="asyncio-stream.html#asyncio.start_server" title="asyncio.start_server"><code class="xref py py-func docutils literal notranslate"><span class="pre">start_server()</span></code></a> function is a higher-level alternative API
that returns a pair of <a class="reference internal" href="asyncio-stream.html#asyncio.StreamReader" title="asyncio.StreamReader"><code class="xref py py-class docutils literal notranslate"><span class="pre">StreamReader</span></code></a> and <a class="reference internal" href="asyncio-stream.html#asyncio.StreamWriter" title="asyncio.StreamWriter"><code class="xref py py-class docutils literal notranslate"><span class="pre">StreamWriter</span></code></a>
that can be used in an async/await code.</p>
</div>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.create_unix_server">
<em class="property"><span class="k"><span class="pre">async</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">create_unix_server</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">protocol_factory</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">path</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="keyword-only-separator o"><abbr title="Keyword-only parameters separator (PEP 3102)"><span class="pre">*</span></abbr></span></em>, <em class="sig-param"><span class="n"><span class="pre">sock</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">backlog</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">100</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">ssl</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">ssl_handshake_timeout</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">ssl_shutdown_timeout</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">start_serving</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">True</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">cleanup_socket</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">True</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.create_unix_server" title="Link to this definition">¶</a></dt>
<dd><p>Similar to <a class="reference internal" href="#asyncio.loop.create_server" title="asyncio.loop.create_server"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_server()</span></code></a> but works with the
<a class="reference internal" href="socket.html#socket.AF_UNIX" title="socket.AF_UNIX"><code class="xref py py-const docutils literal notranslate"><span class="pre">AF_UNIX</span></code></a> socket family.</p>
<p><em>path</em> is the name of a Unix domain socket, and is required,
unless a <em>sock</em> argument is provided. Abstract Unix sockets,
<a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a>, <a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a>, and <a class="reference internal" href="pathlib.html#pathlib.Path" title="pathlib.Path"><code class="xref py py-class docutils literal notranslate"><span class="pre">Path</span></code></a> paths
are supported.</p>
<p>If <em>cleanup_socket</em> is true then the Unix socket will automatically
be removed from the filesystem when the server is closed, unless the
socket has been replaced after the server has been created.</p>
<p>See the documentation of the <a class="reference internal" href="#asyncio.loop.create_server" title="asyncio.loop.create_server"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_server()</span></code></a> method
for information about arguments to this method.</p>
<div class="availability docutils container">
<p><a class="reference internal" href="intro.html#availability"><span class="std std-ref">Availability</span></a>: Unix.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.7: </span>Added the <em>ssl_handshake_timeout</em> and <em>start_serving</em> parameters.
The <em>path</em> parameter can now be a <a class="reference internal" href="pathlib.html#pathlib.Path" title="pathlib.Path"><code class="xref py py-class docutils literal notranslate"><span class="pre">Path</span></code></a> object.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.11: </span>Added the <em>ssl_shutdown_timeout</em> parameter.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.13: </span>Added the <em>cleanup_socket</em> parameter.</p>
</div>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.connect_accepted_socket">
<em class="property"><span class="k"><span class="pre">async</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">connect_accepted_socket</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">protocol_factory</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">sock</span></span></em>, <em class="sig-param"><span class="keyword-only-separator o"><abbr title="Keyword-only parameters separator (PEP 3102)"><span class="pre">*</span></abbr></span></em>, <em class="sig-param"><span class="n"><span class="pre">ssl</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">ssl_handshake_timeout</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">ssl_shutdown_timeout</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.connect_accepted_socket" title="Link to this definition">¶</a></dt>
<dd><p>Wrap an already accepted connection into a transport/protocol pair.</p>
<p>This method can be used by servers that accept connections outside
of asyncio but that use asyncio to handle them.</p>
<p>Parameters:</p>
<ul>
<li><p><em>protocol_factory</em> must be a callable returning a
<a class="reference internal" href="asyncio-protocol.html#asyncio-protocol"><span class="std std-ref">protocol</span></a> implementation.</p></li>
<li><p><em>sock</em> is a preexisting socket object returned from
<a class="reference internal" href="socket.html#socket.socket.accept" title="socket.socket.accept"><code class="xref py py-meth docutils literal notranslate"><span class="pre">socket.accept</span></code></a>.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>The <em>sock</em> argument transfers ownership of the socket to the
transport created. To close the socket, call the transport’s
<a class="reference internal" href="asyncio-protocol.html#asyncio.BaseTransport.close" title="asyncio.BaseTransport.close"><code class="xref py py-meth docutils literal notranslate"><span class="pre">close()</span></code></a> method.</p>
</div>
</li>
<li><p><em>ssl</em> can be set to an <a class="reference internal" href="ssl.html#ssl.SSLContext" title="ssl.SSLContext"><code class="xref py py-class docutils literal notranslate"><span class="pre">SSLContext</span></code></a> to enable SSL over
the accepted connections.</p></li>
<li><p><em>ssl_handshake_timeout</em> is (for an SSL connection) the time in seconds to
wait for the SSL handshake to complete before aborting the connection.
<code class="docutils literal notranslate"><span class="pre">60.0</span></code> seconds if <code class="docutils literal notranslate"><span class="pre">None</span></code> (default).</p></li>
<li><p><em>ssl_shutdown_timeout</em> is the time in seconds to wait for the SSL shutdown
to complete before aborting the connection. <code class="docutils literal notranslate"><span class="pre">30.0</span></code> seconds if <code class="docutils literal notranslate"><span class="pre">None</span></code>
(default).</p></li>
</ul>
<p>Returns a <code class="docutils literal notranslate"><span class="pre">(transport,</span> <span class="pre">protocol)</span></code> pair.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.5.3.</span></p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.7: </span>Added the <em>ssl_handshake_timeout</em> parameter.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.11: </span>Added the <em>ssl_shutdown_timeout</em> parameter.</p>
</div>
</dd></dl>
</section>
<section id="transferring-files">
<h3><a class="toc-backref" href="#id7" role="doc-backlink">Transferring files</a><a class="headerlink" href="#transferring-files" title="Link to this heading">¶</a></h3>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.sendfile">
<em class="property"><span class="k"><span class="pre">async</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">sendfile</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">transport</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">file</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">offset</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">0</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">count</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="keyword-only-separator o"><abbr title="Keyword-only parameters separator (PEP 3102)"><span class="pre">*</span></abbr></span></em>, <em class="sig-param"><span class="n"><span class="pre">fallback</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">True</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.sendfile" title="Link to this definition">¶</a></dt>
<dd><p>Send a <em>file</em> over a <em>transport</em>. Return the total number of bytes
sent.</p>
<p>The method uses high-performance <a class="reference internal" href="os.html#os.sendfile" title="os.sendfile"><code class="xref py py-meth docutils literal notranslate"><span class="pre">os.sendfile()</span></code></a> if available.</p>
<p><em>file</em> must be a regular file object opened in binary mode.</p>
<p><em>offset</em> tells from where to start reading the file. If specified,
<em>count</em> is the total number of bytes to transmit as opposed to
sending the file until EOF is reached. File position is always updated,
even when this method raises an error, and
<a class="reference internal" href="io.html#io.IOBase.tell" title="io.IOBase.tell"><code class="xref py py-meth docutils literal notranslate"><span class="pre">file.tell()</span></code></a> can be used to obtain the actual
number of bytes sent.</p>
<p><em>fallback</em> set to <code class="docutils literal notranslate"><span class="pre">True</span></code> makes asyncio to manually read and send
the file when the platform does not support the sendfile system call
(e.g. Windows or SSL socket on Unix).</p>
<p>Raise <a class="reference internal" href="asyncio-exceptions.html#asyncio.SendfileNotAvailableError" title="asyncio.SendfileNotAvailableError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">SendfileNotAvailableError</span></code></a> if the system does not support
the <em>sendfile</em> syscall and <em>fallback</em> is <code class="docutils literal notranslate"><span class="pre">False</span></code>.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.7.</span></p>
</div>
</dd></dl>
</section>
<section id="tls-upgrade">
<h3><a class="toc-backref" href="#id8" role="doc-backlink">TLS Upgrade</a><a class="headerlink" href="#tls-upgrade" title="Link to this heading">¶</a></h3>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.start_tls">
<em class="property"><span class="k"><span class="pre">async</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">start_tls</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">transport</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">protocol</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">sslcontext</span></span></em>, <em class="sig-param"><span class="keyword-only-separator o"><abbr title="Keyword-only parameters separator (PEP 3102)"><span class="pre">*</span></abbr></span></em>, <em class="sig-param"><span class="n"><span class="pre">server_side</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">False</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">server_hostname</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">ssl_handshake_timeout</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">ssl_shutdown_timeout</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.start_tls" title="Link to this definition">¶</a></dt>
<dd><p>Upgrade an existing transport-based connection to TLS.</p>
<p>Create a TLS coder/decoder instance and insert it between the <em>transport</em>
and the <em>protocol</em>. The coder/decoder implements both <em>transport</em>-facing
protocol and <em>protocol</em>-facing transport.</p>
<p>Return the created two-interface instance. After <em>await</em>, the <em>protocol</em>
must stop using the original <em>transport</em> and communicate with the returned
object only because the coder caches <em>protocol</em>-side data and sporadically
exchanges extra TLS session packets with <em>transport</em>.</p>
<p>In some situations (e.g. when the passed transport is already closing) this
may return <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p>
<p>Parameters:</p>
<ul class="simple">
<li><p><em>transport</em> and <em>protocol</em> instances that methods like
<a class="reference internal" href="#asyncio.loop.create_server" title="asyncio.loop.create_server"><code class="xref py py-meth docutils literal notranslate"><span class="pre">create_server()</span></code></a> and
<a class="reference internal" href="#asyncio.loop.create_connection" title="asyncio.loop.create_connection"><code class="xref py py-meth docutils literal notranslate"><span class="pre">create_connection()</span></code></a> return.</p></li>
<li><p><em>sslcontext</em>: a configured instance of <a class="reference internal" href="ssl.html#ssl.SSLContext" title="ssl.SSLContext"><code class="xref py py-class docutils literal notranslate"><span class="pre">SSLContext</span></code></a>.</p></li>
<li><p><em>server_side</em> pass <code class="docutils literal notranslate"><span class="pre">True</span></code> when a server-side connection is being
upgraded (like the one created by <a class="reference internal" href="#asyncio.loop.create_server" title="asyncio.loop.create_server"><code class="xref py py-meth docutils literal notranslate"><span class="pre">create_server()</span></code></a>).</p></li>
<li><p><em>server_hostname</em>: sets or overrides the host name that the target
server’s certificate will be matched against.</p></li>
<li><p><em>ssl_handshake_timeout</em> is (for a TLS connection) the time in seconds to
wait for the TLS handshake to complete before aborting the connection.
<code class="docutils literal notranslate"><span class="pre">60.0</span></code> seconds if <code class="docutils literal notranslate"><span class="pre">None</span></code> (default).</p></li>
<li><p><em>ssl_shutdown_timeout</em> is the time in seconds to wait for the SSL shutdown
to complete before aborting the connection. <code class="docutils literal notranslate"><span class="pre">30.0</span></code> seconds if <code class="docutils literal notranslate"><span class="pre">None</span></code>
(default).</p></li>
</ul>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.7.</span></p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.11: </span>Added the <em>ssl_shutdown_timeout</em> parameter.</p>
</div>
</dd></dl>
</section>
<section id="watching-file-descriptors">
<h3><a class="toc-backref" href="#id9" role="doc-backlink">Watching file descriptors</a><a class="headerlink" href="#watching-file-descriptors" title="Link to this heading">¶</a></h3>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.add_reader">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">add_reader</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">fd</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">callback</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">*</span></span><span class="n"><span class="pre">args</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.add_reader" title="Link to this definition">¶</a></dt>
<dd><p>Start monitoring the <em>fd</em> file descriptor for read availability and
invoke <em>callback</em> with the specified arguments once <em>fd</em> is available for
reading.</p>
<p>Any preexisting callback registered for <em>fd</em> is cancelled and replaced by
<em>callback</em>.</p>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.remove_reader">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">remove_reader</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">fd</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.remove_reader" title="Link to this definition">¶</a></dt>
<dd><p>Stop monitoring the <em>fd</em> file descriptor for read availability. Returns
<code class="docutils literal notranslate"><span class="pre">True</span></code> if <em>fd</em> was previously being monitored for reads.</p>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.add_writer">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">add_writer</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">fd</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">callback</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">*</span></span><span class="n"><span class="pre">args</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.add_writer" title="Link to this definition">¶</a></dt>
<dd><p>Start monitoring the <em>fd</em> file descriptor for write availability and
invoke <em>callback</em> with the specified arguments <em>args</em> once <em>fd</em> is
available for writing.</p>
<p>Any preexisting callback registered for <em>fd</em> is cancelled and replaced by
<em>callback</em>.</p>
<p>Use <a class="reference internal" href="functools.html#functools.partial" title="functools.partial"><code class="xref py py-func docutils literal notranslate"><span class="pre">functools.partial()</span></code></a> <a class="reference internal" href="#asyncio-pass-keywords"><span class="std std-ref">to pass keyword arguments</span></a> to <em>callback</em>.</p>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.remove_writer">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">remove_writer</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">fd</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.remove_writer" title="Link to this definition">¶</a></dt>
<dd><p>Stop monitoring the <em>fd</em> file descriptor for write availability. Returns
<code class="docutils literal notranslate"><span class="pre">True</span></code> if <em>fd</em> was previously being monitored for writes.</p>
</dd></dl>
<p>See also <a class="reference internal" href="asyncio-platforms.html#asyncio-platform-support"><span class="std std-ref">Platform Support</span></a> section
for some limitations of these methods.</p>
</section>
<section id="working-with-socket-objects-directly">
<h3><a class="toc-backref" href="#id10" role="doc-backlink">Working with socket objects directly</a><a class="headerlink" href="#working-with-socket-objects-directly" title="Link to this heading">¶</a></h3>
<p>In general, protocol implementations that use transport-based APIs
such as <a class="reference internal" href="#asyncio.loop.create_connection" title="asyncio.loop.create_connection"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_connection()</span></code></a> and <a class="reference internal" href="#asyncio.loop.create_server" title="asyncio.loop.create_server"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_server()</span></code></a>
are faster than implementations that work with sockets directly.
However, there are some use cases when performance is not critical, and
working with <a class="reference internal" href="socket.html#socket.socket" title="socket.socket"><code class="xref py py-class docutils literal notranslate"><span class="pre">socket</span></code></a> objects directly is more
convenient.</p>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.sock_recv">
<em class="property"><span class="k"><span class="pre">async</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">sock_recv</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">sock</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">nbytes</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.sock_recv" title="Link to this definition">¶</a></dt>
<dd><p>Receive up to <em>nbytes</em> from <em>sock</em>. Asynchronous version of
<a class="reference internal" href="socket.html#socket.socket.recv" title="socket.socket.recv"><code class="xref py py-meth docutils literal notranslate"><span class="pre">socket.recv()</span></code></a>.</p>
<p>Return the received data as a bytes object.</p>
<p><em>sock</em> must be a non-blocking socket.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.7: </span>Even though this method was always documented as a coroutine
method, releases before Python 3.7 returned a <a class="reference internal" href="asyncio-future.html#asyncio.Future" title="asyncio.Future"><code class="xref py py-class docutils literal notranslate"><span class="pre">Future</span></code></a>.
Since Python 3.7 this is an <code class="docutils literal notranslate"><span class="pre">async</span> <span class="pre">def</span></code> method.</p>
</div>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.sock_recv_into">
<em class="property"><span class="k"><span class="pre">async</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">sock_recv_into</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">sock</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">buf</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.sock_recv_into" title="Link to this definition">¶</a></dt>
<dd><p>Receive data from <em>sock</em> into the <em>buf</em> buffer. Modeled after the blocking
<a class="reference internal" href="socket.html#socket.socket.recv_into" title="socket.socket.recv_into"><code class="xref py py-meth docutils literal notranslate"><span class="pre">socket.recv_into()</span></code></a> method.</p>
<p>Return the number of bytes written to the buffer.</p>
<p><em>sock</em> must be a non-blocking socket.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.7.</span></p>
</div>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.sock_recvfrom">
<em class="property"><span class="k"><span class="pre">async</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">sock_recvfrom</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">sock</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">bufsize</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.sock_recvfrom" title="Link to this definition">¶</a></dt>
<dd><p>Receive a datagram of up to <em>bufsize</em> from <em>sock</em>. Asynchronous version of
<a class="reference internal" href="socket.html#socket.socket.recvfrom" title="socket.socket.recvfrom"><code class="xref py py-meth docutils literal notranslate"><span class="pre">socket.recvfrom()</span></code></a>.</p>
<p>Return a tuple of (received data, remote address).</p>
<p><em>sock</em> must be a non-blocking socket.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.11.</span></p>
</div>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.sock_recvfrom_into">
<em class="property"><span class="k"><span class="pre">async</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">sock_recvfrom_into</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">sock</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">buf</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">nbytes</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">0</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.sock_recvfrom_into" title="Link to this definition">¶</a></dt>
<dd><p>Receive a datagram of up to <em>nbytes</em> from <em>sock</em> into <em>buf</em>.
Asynchronous version of
<a class="reference internal" href="socket.html#socket.socket.recvfrom_into" title="socket.socket.recvfrom_into"><code class="xref py py-meth docutils literal notranslate"><span class="pre">socket.recvfrom_into()</span></code></a>.</p>
<p>Return a tuple of (number of bytes received, remote address).</p>
<p><em>sock</em> must be a non-blocking socket.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.11.</span></p>
</div>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.sock_sendall">
<em class="property"><span class="k"><span class="pre">async</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">sock_sendall</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">sock</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">data</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.sock_sendall" title="Link to this definition">¶</a></dt>
<dd><p>Send <em>data</em> to the <em>sock</em> socket. Asynchronous version of
<a class="reference internal" href="socket.html#socket.socket.sendall" title="socket.socket.sendall"><code class="xref py py-meth docutils literal notranslate"><span class="pre">socket.sendall()</span></code></a>.</p>
<p>This method continues to send to the socket until either all data
in <em>data</em> has been sent or an error occurs. <code class="docutils literal notranslate"><span class="pre">None</span></code> is returned
on success. On error, an exception is raised. Additionally, there is no way
to determine how much data, if any, was successfully processed by the
receiving end of the connection.</p>
<p><em>sock</em> must be a non-blocking socket.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.7: </span>Even though the method was always documented as a coroutine
method, before Python 3.7 it returned a <a class="reference internal" href="asyncio-future.html#asyncio.Future" title="asyncio.Future"><code class="xref py py-class docutils literal notranslate"><span class="pre">Future</span></code></a>.
Since Python 3.7, this is an <code class="docutils literal notranslate"><span class="pre">async</span> <span class="pre">def</span></code> method.</p>
</div>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.sock_sendto">
<em class="property"><span class="k"><span class="pre">async</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">sock_sendto</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">sock</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">data</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">address</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.sock_sendto" title="Link to this definition">¶</a></dt>
<dd><p>Send a datagram from <em>sock</em> to <em>address</em>.
Asynchronous version of
<a class="reference internal" href="socket.html#socket.socket.sendto" title="socket.socket.sendto"><code class="xref py py-meth docutils literal notranslate"><span class="pre">socket.sendto()</span></code></a>.</p>
<p>Return the number of bytes sent.</p>
<p><em>sock</em> must be a non-blocking socket.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.11.</span></p>
</div>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.sock_connect">
<em class="property"><span class="k"><span class="pre">async</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">sock_connect</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">sock</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">address</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.sock_connect" title="Link to this definition">¶</a></dt>
<dd><p>Connect <em>sock</em> to a remote socket at <em>address</em>.</p>
<p>Asynchronous version of <a class="reference internal" href="socket.html#socket.socket.connect" title="socket.socket.connect"><code class="xref py py-meth docutils literal notranslate"><span class="pre">socket.connect()</span></code></a>.</p>
<p><em>sock</em> must be a non-blocking socket.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.5.2: </span><code class="docutils literal notranslate"><span class="pre">address</span></code> no longer needs to be resolved. <code class="docutils literal notranslate"><span class="pre">sock_connect</span></code>
will try to check if the <em>address</em> is already resolved by calling
<a class="reference internal" href="socket.html#socket.inet_pton" title="socket.inet_pton"><code class="xref py py-func docutils literal notranslate"><span class="pre">socket.inet_pton()</span></code></a>. If not,
<a class="reference internal" href="#asyncio.loop.getaddrinfo" title="asyncio.loop.getaddrinfo"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.getaddrinfo()</span></code></a> will be used to resolve the
<em>address</em>.</p>
</div>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<p><a class="reference internal" href="#asyncio.loop.create_connection" title="asyncio.loop.create_connection"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_connection()</span></code></a>
and <a class="reference internal" href="asyncio-stream.html#asyncio.open_connection" title="asyncio.open_connection"><code class="xref py py-func docutils literal notranslate"><span class="pre">asyncio.open_connection()</span></code></a>.</p>
</div>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.sock_accept">
<em class="property"><span class="k"><span class="pre">async</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">sock_accept</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">sock</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.sock_accept" title="Link to this definition">¶</a></dt>
<dd><p>Accept a connection. Modeled after the blocking
<a class="reference internal" href="socket.html#socket.socket.accept" title="socket.socket.accept"><code class="xref py py-meth docutils literal notranslate"><span class="pre">socket.accept()</span></code></a> method.</p>
<p>The socket must be bound to an address and listening
for connections. The return value is a pair <code class="docutils literal notranslate"><span class="pre">(conn,</span> <span class="pre">address)</span></code> where <em>conn</em>
is a <em>new</em> socket object usable to send and receive data on the connection,
and <em>address</em> is the address bound to the socket on the other end of the
connection.</p>
<p><em>sock</em> must be a non-blocking socket.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.7: </span>Even though the method was always documented as a coroutine
method, before Python 3.7 it returned a <a class="reference internal" href="asyncio-future.html#asyncio.Future" title="asyncio.Future"><code class="xref py py-class docutils literal notranslate"><span class="pre">Future</span></code></a>.
Since Python 3.7, this is an <code class="docutils literal notranslate"><span class="pre">async</span> <span class="pre">def</span></code> method.</p>
</div>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<p><a class="reference internal" href="#asyncio.loop.create_server" title="asyncio.loop.create_server"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_server()</span></code></a> and <a class="reference internal" href="asyncio-stream.html#asyncio.start_server" title="asyncio.start_server"><code class="xref py py-func docutils literal notranslate"><span class="pre">start_server()</span></code></a>.</p>
</div>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.sock_sendfile">
<em class="property"><span class="k"><span class="pre">async</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">sock_sendfile</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">sock</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">file</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">offset</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">0</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">count</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="keyword-only-separator o"><abbr title="Keyword-only parameters separator (PEP 3102)"><span class="pre">*</span></abbr></span></em>, <em class="sig-param"><span class="n"><span class="pre">fallback</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">True</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.sock_sendfile" title="Link to this definition">¶</a></dt>
<dd><p>Send a file using high-performance <a class="reference internal" href="os.html#os.sendfile" title="os.sendfile"><code class="xref py py-mod docutils literal notranslate"><span class="pre">os.sendfile</span></code></a> if possible.
Return the total number of bytes sent.</p>
<p>Asynchronous version of <a class="reference internal" href="socket.html#socket.socket.sendfile" title="socket.socket.sendfile"><code class="xref py py-meth docutils literal notranslate"><span class="pre">socket.sendfile()</span></code></a>.</p>
<p><em>sock</em> must be a non-blocking <a class="reference internal" href="socket.html#socket.SOCK_STREAM" title="socket.SOCK_STREAM"><code class="xref py py-const docutils literal notranslate"><span class="pre">socket.SOCK_STREAM</span></code></a>
<a class="reference internal" href="socket.html#socket.socket" title="socket.socket"><code class="xref py py-class docutils literal notranslate"><span class="pre">socket</span></code></a>.</p>
<p><em>file</em> must be a regular file object open in binary mode.</p>
<p><em>offset</em> tells from where to start reading the file. If specified,
<em>count</em> is the total number of bytes to transmit as opposed to
sending the file until EOF is reached. File position is always updated,
even when this method raises an error, and
<a class="reference internal" href="io.html#io.IOBase.tell" title="io.IOBase.tell"><code class="xref py py-meth docutils literal notranslate"><span class="pre">file.tell()</span></code></a> can be used to obtain the actual
number of bytes sent.</p>
<p><em>fallback</em>, when set to <code class="docutils literal notranslate"><span class="pre">True</span></code>, makes asyncio manually read and send
the file when the platform does not support the sendfile syscall
(e.g. Windows or SSL socket on Unix).</p>
<p>Raise <a class="reference internal" href="asyncio-exceptions.html#asyncio.SendfileNotAvailableError" title="asyncio.SendfileNotAvailableError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">SendfileNotAvailableError</span></code></a> if the system does not support
<em>sendfile</em> syscall and <em>fallback</em> is <code class="docutils literal notranslate"><span class="pre">False</span></code>.</p>
<p><em>sock</em> must be a non-blocking socket.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.7.</span></p>
</div>
</dd></dl>
</section>
<section id="dns">
<h3><a class="toc-backref" href="#id11" role="doc-backlink">DNS</a><a class="headerlink" href="#dns" title="Link to this heading">¶</a></h3>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.getaddrinfo">
<em class="property"><span class="k"><span class="pre">async</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">getaddrinfo</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">host</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">port</span></span></em>, <em class="sig-param"><span class="keyword-only-separator o"><abbr title="Keyword-only parameters separator (PEP 3102)"><span class="pre">*</span></abbr></span></em>, <em class="sig-param"><span class="n"><span class="pre">family</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">0</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">type</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">0</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">proto</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">0</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">flags</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">0</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.getaddrinfo" title="Link to this definition">¶</a></dt>
<dd><p>Asynchronous version of <a class="reference internal" href="socket.html#socket.getaddrinfo" title="socket.getaddrinfo"><code class="xref py py-meth docutils literal notranslate"><span class="pre">socket.getaddrinfo()</span></code></a>.</p>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.getnameinfo">
<em class="property"><span class="k"><span class="pre">async</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">getnameinfo</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">sockaddr</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">flags</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">0</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.getnameinfo" title="Link to this definition">¶</a></dt>
<dd><p>Asynchronous version of <a class="reference internal" href="socket.html#socket.getnameinfo" title="socket.getnameinfo"><code class="xref py py-meth docutils literal notranslate"><span class="pre">socket.getnameinfo()</span></code></a>.</p>
</dd></dl>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>Both <em>getaddrinfo</em> and <em>getnameinfo</em> internally utilize their synchronous
versions through the loop’s default thread pool executor.
When this executor is saturated, these methods may experience delays,
which higher-level networking libraries may report as increased timeouts.
To mitigate this, consider using a custom executor for other user tasks,
or setting a default executor with a larger number of workers.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.7: </span>Both <em>getaddrinfo</em> and <em>getnameinfo</em> methods were always documented
to return a coroutine, but prior to Python 3.7 they were, in fact,
returning <a class="reference internal" href="asyncio-future.html#asyncio.Future" title="asyncio.Future"><code class="xref py py-class docutils literal notranslate"><span class="pre">asyncio.Future</span></code></a> objects. Starting with Python 3.7
both methods are coroutines.</p>
</div>
</section>
<section id="working-with-pipes">
<h3><a class="toc-backref" href="#id12" role="doc-backlink">Working with pipes</a><a class="headerlink" href="#working-with-pipes" title="Link to this heading">¶</a></h3>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.connect_read_pipe">
<em class="property"><span class="k"><span class="pre">async</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">connect_read_pipe</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">protocol_factory</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">pipe</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.connect_read_pipe" title="Link to this definition">¶</a></dt>
<dd><p>Register the read end of <em>pipe</em> in the event loop.</p>
<p><em>protocol_factory</em> must be a callable returning an
<a class="reference internal" href="asyncio-protocol.html#asyncio-protocol"><span class="std std-ref">asyncio protocol</span></a> implementation.</p>
<p><em>pipe</em> is a <a class="reference internal" href="../glossary.html#term-file-object"><span class="xref std std-term">file-like object</span></a>.</p>
<p>Return pair <code class="docutils literal notranslate"><span class="pre">(transport,</span> <span class="pre">protocol)</span></code>, where <em>transport</em> supports
the <a class="reference internal" href="asyncio-protocol.html#asyncio.ReadTransport" title="asyncio.ReadTransport"><code class="xref py py-class docutils literal notranslate"><span class="pre">ReadTransport</span></code></a> interface and <em>protocol</em> is an object
instantiated by the <em>protocol_factory</em>.</p>
<p>With <a class="reference internal" href="#asyncio.SelectorEventLoop" title="asyncio.SelectorEventLoop"><code class="xref py py-class docutils literal notranslate"><span class="pre">SelectorEventLoop</span></code></a> event loop, the <em>pipe</em> is set to
non-blocking mode.</p>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.connect_write_pipe">
<em class="property"><span class="k"><span class="pre">async</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">connect_write_pipe</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">protocol_factory</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">pipe</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.connect_write_pipe" title="Link to this definition">¶</a></dt>
<dd><p>Register the write end of <em>pipe</em> in the event loop.</p>
<p><em>protocol_factory</em> must be a callable returning an
<a class="reference internal" href="asyncio-protocol.html#asyncio-protocol"><span class="std std-ref">asyncio protocol</span></a> implementation.</p>
<p><em>pipe</em> is <a class="reference internal" href="../glossary.html#term-file-object"><span class="xref std std-term">file-like object</span></a>.</p>
<p>Return pair <code class="docutils literal notranslate"><span class="pre">(transport,</span> <span class="pre">protocol)</span></code>, where <em>transport</em> supports
<a class="reference internal" href="asyncio-protocol.html#asyncio.WriteTransport" title="asyncio.WriteTransport"><code class="xref py py-class docutils literal notranslate"><span class="pre">WriteTransport</span></code></a> interface and <em>protocol</em> is an object
instantiated by the <em>protocol_factory</em>.</p>
<p>With <a class="reference internal" href="#asyncio.SelectorEventLoop" title="asyncio.SelectorEventLoop"><code class="xref py py-class docutils literal notranslate"><span class="pre">SelectorEventLoop</span></code></a> event loop, the <em>pipe</em> is set to
non-blocking mode.</p>
</dd></dl>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p><a class="reference internal" href="#asyncio.SelectorEventLoop" title="asyncio.SelectorEventLoop"><code class="xref py py-class docutils literal notranslate"><span class="pre">SelectorEventLoop</span></code></a> does not support the above methods on
Windows. Use <a class="reference internal" href="#asyncio.ProactorEventLoop" title="asyncio.ProactorEventLoop"><code class="xref py py-class docutils literal notranslate"><span class="pre">ProactorEventLoop</span></code></a> instead for Windows.</p>
</div>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<p>The <a class="reference internal" href="#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.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> methods.</p>
</div>
</section>
<section id="unix-signals">
<h3><a class="toc-backref" href="#id13" role="doc-backlink">Unix signals</a><a class="headerlink" href="#unix-signals" title="Link to this heading">¶</a></h3>
<dl class="py method" id="loop-add-signal-handler">
<dt class="sig sig-object py" id="asyncio.loop.add_signal_handler">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">add_signal_handler</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">signum</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">callback</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">*</span></span><span class="n"><span class="pre">args</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.add_signal_handler" title="Link to this definition">¶</a></dt>
<dd><p>Set <em>callback</em> as the handler for the <em>signum</em> signal,
passing <em>args</em> as positional arguments.</p>
<p>The callback will be invoked by <em>loop</em>, along with other queued callbacks
and runnable coroutines of that event loop. Unlike signal handlers
registered using <a class="reference internal" href="signal.html#signal.signal" title="signal.signal"><code class="xref py py-func docutils literal notranslate"><span class="pre">signal.signal()</span></code></a>, a callback registered with this
function is allowed to interact with the event loop.</p>
<p>Raise <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ValueError</span></code></a> if the signal number is invalid or uncatchable.
Raise <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 a problem setting up the handler.</p>
<p>Use <a class="reference internal" href="functools.html#functools.partial" title="functools.partial"><code class="xref py py-func docutils literal notranslate"><span class="pre">functools.partial()</span></code></a> <a class="reference internal" href="#asyncio-pass-keywords"><span class="std std-ref">to pass keyword arguments</span></a> to <em>callback</em>.</p>
<p>Like <a class="reference internal" href="signal.html#signal.signal" title="signal.signal"><code class="xref py py-func docutils literal notranslate"><span class="pre">signal.signal()</span></code></a>, this function must be invoked in the main
thread.</p>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.remove_signal_handler">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">remove_signal_handler</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">sig</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.remove_signal_handler" title="Link to this definition">¶</a></dt>
<dd><p>Remove the handler for the <em>sig</em> signal.</p>
<p>Return <code class="docutils literal notranslate"><span class="pre">True</span></code> if the signal handler was removed, or <code class="docutils literal notranslate"><span class="pre">False</span></code> if
no handler was set for the given signal.</p>
<div class="availability docutils container">
<p><a class="reference internal" href="intro.html#availability"><span class="std std-ref">Availability</span></a>: Unix.</p>
</div>
</dd></dl>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<p>The <a class="reference internal" href="signal.html#module-signal" title="signal: Set handlers for asynchronous events."><code class="xref py py-mod docutils literal notranslate"><span class="pre">signal</span></code></a> module.</p>
</div>
</section>
<section id="executing-code-in-thread-or-process-pools">
<h3><a class="toc-backref" href="#id14" role="doc-backlink">Executing code in thread or process pools</a><a class="headerlink" href="#executing-code-in-thread-or-process-pools" title="Link to this heading">¶</a></h3>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.run_in_executor">
<em class="property"><span class="pre">awaitable</span> </em><span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">run_in_executor</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">executor</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">func</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">*</span></span><span class="n"><span class="pre">args</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.run_in_executor" title="Link to this definition">¶</a></dt>
<dd><p>Arrange for <em>func</em> to be called in the specified executor
passing <em>args</em> as positional arguments.</p>
<p>The <em>executor</em> argument should be an <a class="reference internal" href="concurrent.futures.html#concurrent.futures.Executor" title="concurrent.futures.Executor"><code class="xref py py-class docutils literal notranslate"><span class="pre">concurrent.futures.Executor</span></code></a>
instance. The default executor is used if <em>executor</em> is <code class="docutils literal notranslate"><span class="pre">None</span></code>.
The default executor can be set by <a class="reference internal" href="#asyncio.loop.set_default_executor" title="asyncio.loop.set_default_executor"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.set_default_executor()</span></code></a>,
otherwise, a <a class="reference internal" href="concurrent.futures.html#concurrent.futures.ThreadPoolExecutor" title="concurrent.futures.ThreadPoolExecutor"><code class="xref py py-class docutils literal notranslate"><span class="pre">concurrent.futures.ThreadPoolExecutor</span></code></a> will be
lazy-initialized and used by <a class="reference internal" href="#asyncio.loop.run_in_executor" title="asyncio.loop.run_in_executor"><code class="xref py py-func docutils literal notranslate"><span class="pre">run_in_executor()</span></code></a> if needed.</p>
<p>Example:</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="kn">import</span><span class="w"> </span><span class="nn">concurrent.futures</span>
<span class="k">def</span><span class="w"> </span><span class="nf">blocking_io</span><span class="p">():</span>
<span class="c1"># File operations (such as logging) can block the</span>
<span class="c1"># event loop: run them in a thread pool.</span>
<span class="k">with</span> <span class="nb">open</span><span class="p">(</span><span class="s1">'/dev/urandom'</span><span class="p">,</span> <span class="s1">'rb'</span><span class="p">)</span> <span class="k">as</span> <span class="n">f</span><span class="p">:</span>
<span class="k">return</span> <span class="n">f</span><span class="o">.</span><span class="n">read</span><span class="p">(</span><span class="mi">100</span><span class="p">)</span>
<span class="k">def</span><span class="w"> </span><span class="nf">cpu_bound</span><span class="p">():</span>
<span class="c1"># CPU-bound operations will block the event loop:</span>
<span class="c1"># in general it is preferable to run them in a</span>
<span class="c1"># process pool.</span>
<span class="k">return</span> <span class="nb">sum</span><span class="p">(</span><span class="n">i</span> <span class="o">*</span> <span class="n">i</span> <span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">10</span> <span class="o">**</span> <span class="mi">7</span><span class="p">))</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="n">loop</span> <span class="o">=</span> <span class="n">asyncio</span><span class="o">.</span><span class="n">get_running_loop</span><span class="p">()</span>
<span class="c1">## Options:</span>
<span class="c1"># 1. Run in the default loop's executor:</span>
<span class="n">result</span> <span class="o">=</span> <span class="k">await</span> <span class="n">loop</span><span class="o">.</span><span class="n">run_in_executor</span><span class="p">(</span>
<span class="kc">None</span><span class="p">,</span> <span class="n">blocking_io</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="s1">'default thread pool'</span><span class="p">,</span> <span class="n">result</span><span class="p">)</span>
<span class="c1"># 2. Run in a custom thread pool:</span>
<span class="k">with</span> <span class="n">concurrent</span><span class="o">.</span><span class="n">futures</span><span class="o">.</span><span class="n">ThreadPoolExecutor</span><span class="p">()</span> <span class="k">as</span> <span class="n">pool</span><span class="p">:</span>
<span class="n">result</span> <span class="o">=</span> <span class="k">await</span> <span class="n">loop</span><span class="o">.</span><span class="n">run_in_executor</span><span class="p">(</span>
<span class="n">pool</span><span class="p">,</span> <span class="n">blocking_io</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="s1">'custom thread pool'</span><span class="p">,</span> <span class="n">result</span><span class="p">)</span>
<span class="c1"># 3. Run in a custom process pool:</span>
<span class="k">with</span> <span class="n">concurrent</span><span class="o">.</span><span class="n">futures</span><span class="o">.</span><span class="n">ProcessPoolExecutor</span><span class="p">()</span> <span class="k">as</span> <span class="n">pool</span><span class="p">:</span>
<span class="n">result</span> <span class="o">=</span> <span class="k">await</span> <span class="n">loop</span><span class="o">.</span><span class="n">run_in_executor</span><span class="p">(</span>
<span class="n">pool</span><span class="p">,</span> <span class="n">cpu_bound</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="s1">'custom process pool'</span><span class="p">,</span> <span class="n">result</span><span class="p">)</span>
<span class="c1"># 4. Run in a custom interpreter pool:</span>
<span class="k">with</span> <span class="n">concurrent</span><span class="o">.</span><span class="n">futures</span><span class="o">.</span><span class="n">InterpreterPoolExecutor</span><span class="p">()</span> <span class="k">as</span> <span class="n">pool</span><span class="p">:</span>
<span class="n">result</span> <span class="o">=</span> <span class="k">await</span> <span class="n">loop</span><span class="o">.</span><span class="n">run_in_executor</span><span class="p">(</span>
<span class="n">pool</span><span class="p">,</span> <span class="n">cpu_bound</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="s1">'custom interpreter pool'</span><span class="p">,</span> <span class="n">result</span><span class="p">)</span>
<span class="k">if</span> <span class="vm">__name__</span> <span class="o">==</span> <span class="s1">'__main__'</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>
<p>Note that the entry point guard (<code class="docutils literal notranslate"><span class="pre">if</span> <span class="pre">__name__</span> <span class="pre">==</span> <span class="pre">'__main__'</span></code>)
is required for option 3 due to the peculiarities of <a class="reference internal" href="multiprocessing.html#module-multiprocessing" title="multiprocessing: Process-based parallelism."><code class="xref py py-mod docutils literal notranslate"><span class="pre">multiprocessing</span></code></a>,
which is used by <a class="reference internal" href="concurrent.futures.html#concurrent.futures.ProcessPoolExecutor" title="concurrent.futures.ProcessPoolExecutor"><code class="xref py py-class docutils literal notranslate"><span class="pre">ProcessPoolExecutor</span></code></a>.
See <a class="reference internal" href="multiprocessing.html#multiprocessing-safe-main-import"><span class="std std-ref">Safe importing of main module</span></a>.</p>
<p>This method returns a <a class="reference internal" href="asyncio-future.html#asyncio.Future" title="asyncio.Future"><code class="xref py py-class docutils literal notranslate"><span class="pre">asyncio.Future</span></code></a> object.</p>
<p>Use <a class="reference internal" href="functools.html#functools.partial" title="functools.partial"><code class="xref py py-func docutils literal notranslate"><span class="pre">functools.partial()</span></code></a> <a class="reference internal" href="#asyncio-pass-keywords"><span class="std std-ref">to pass keyword arguments</span></a> to <em>func</em>.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.5.3: </span><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.run_in_executor()</span></code> no longer configures the
<code class="docutils literal notranslate"><span class="pre">max_workers</span></code> of the thread pool executor it creates, instead
leaving it up to the thread pool executor
(<a class="reference internal" href="concurrent.futures.html#concurrent.futures.ThreadPoolExecutor" title="concurrent.futures.ThreadPoolExecutor"><code class="xref py py-class docutils literal notranslate"><span class="pre">ThreadPoolExecutor</span></code></a>) to set the
default.</p>
</div>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.set_default_executor">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">set_default_executor</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">executor</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.set_default_executor" title="Link to this definition">¶</a></dt>
<dd><p>Set <em>executor</em> as the default executor used by <a class="reference internal" href="#asyncio.loop.run_in_executor" title="asyncio.loop.run_in_executor"><code class="xref py py-meth docutils literal notranslate"><span class="pre">run_in_executor()</span></code></a>.
<em>executor</em> must be an instance of
<a class="reference internal" href="concurrent.futures.html#concurrent.futures.ThreadPoolExecutor" title="concurrent.futures.ThreadPoolExecutor"><code class="xref py py-class docutils literal notranslate"><span class="pre">ThreadPoolExecutor</span></code></a>, which includes
<a class="reference internal" href="concurrent.futures.html#concurrent.futures.InterpreterPoolExecutor" title="concurrent.futures.InterpreterPoolExecutor"><code class="xref py py-class docutils literal notranslate"><span class="pre">InterpreterPoolExecutor</span></code></a>.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.11: </span><em>executor</em> must be an instance of
<a class="reference internal" href="concurrent.futures.html#concurrent.futures.ThreadPoolExecutor" title="concurrent.futures.ThreadPoolExecutor"><code class="xref py py-class docutils literal notranslate"><span class="pre">ThreadPoolExecutor</span></code></a>.</p>
</div>
</dd></dl>
</section>
<section id="error-handling-api">
<h3><a class="toc-backref" href="#id15" role="doc-backlink">Error Handling API</a><a class="headerlink" href="#error-handling-api" title="Link to this heading">¶</a></h3>
<p>Allows customizing how exceptions are handled in the event loop.</p>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.set_exception_handler">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">set_exception_handler</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">handler</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.set_exception_handler" title="Link to this definition">¶</a></dt>
<dd><p>Set <em>handler</em> as the new event loop exception handler.</p>
<p>If <em>handler</em> is <code class="docutils literal notranslate"><span class="pre">None</span></code>, the default exception handler will
be set. Otherwise, <em>handler</em> must be a callable with the signature
matching <code class="docutils literal notranslate"><span class="pre">(loop,</span> <span class="pre">context)</span></code>, where <code class="docutils literal notranslate"><span class="pre">loop</span></code>
is a reference to the active event loop, and <code class="docutils literal notranslate"><span class="pre">context</span></code>
is a <code class="docutils literal notranslate"><span class="pre">dict</span></code> object containing the details of the exception
(see <a class="reference internal" href="#asyncio.loop.call_exception_handler" title="asyncio.loop.call_exception_handler"><code class="xref py py-meth docutils literal notranslate"><span class="pre">call_exception_handler()</span></code></a> documentation for details
about context).</p>
<p>If the handler is called on behalf of a <a class="reference internal" href="asyncio-task.html#asyncio.Task" title="asyncio.Task"><code class="xref py py-class docutils literal notranslate"><span class="pre">Task</span></code></a> or
<a class="reference internal" href="#asyncio.Handle" title="asyncio.Handle"><code class="xref py py-class docutils literal notranslate"><span class="pre">Handle</span></code></a>, it is run in the
<a class="reference internal" href="contextvars.html#contextvars.Context" title="contextvars.Context"><code class="xref py py-class docutils literal notranslate"><span class="pre">contextvars.Context</span></code></a> of that task or callback handle.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.12: </span>The handler may be called in the <a class="reference internal" href="contextvars.html#contextvars.Context" title="contextvars.Context"><code class="xref py py-class docutils literal notranslate"><span class="pre">Context</span></code></a>
of the task or handle where the exception originated.</p>
</div>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.get_exception_handler">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">get_exception_handler</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.get_exception_handler" title="Link to this definition">¶</a></dt>
<dd><p>Return the current exception handler, or <code class="docutils literal notranslate"><span class="pre">None</span></code> if no custom
exception handler was set.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.5.2.</span></p>
</div>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.default_exception_handler">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">default_exception_handler</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">context</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.default_exception_handler" title="Link to this definition">¶</a></dt>
<dd><p>Default exception handler.</p>
<p>This is called when an exception occurs and no exception
handler is set. This can be called by a custom exception
handler that wants to defer to the default handler behavior.</p>
<p><em>context</em> parameter has the same meaning as in
<a class="reference internal" href="#asyncio.loop.call_exception_handler" title="asyncio.loop.call_exception_handler"><code class="xref py py-meth docutils literal notranslate"><span class="pre">call_exception_handler()</span></code></a>.</p>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.call_exception_handler">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">call_exception_handler</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">context</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.call_exception_handler" title="Link to this definition">¶</a></dt>
<dd><p>Call the current event loop exception handler.</p>
<p><em>context</em> is a <code class="docutils literal notranslate"><span class="pre">dict</span></code> object containing the following keys
(new keys may be introduced in future Python versions):</p>
<ul class="simple">
<li><p>‘message’: Error message;</p></li>
<li><p>‘exception’ (optional): Exception object;</p></li>
<li><p>‘future’ (optional): <a class="reference internal" href="asyncio-future.html#asyncio.Future" title="asyncio.Future"><code class="xref py py-class docutils literal notranslate"><span class="pre">asyncio.Future</span></code></a> instance;</p></li>
<li><p>‘task’ (optional): <a class="reference internal" href="asyncio-task.html#asyncio.Task" title="asyncio.Task"><code class="xref py py-class docutils literal notranslate"><span class="pre">asyncio.Task</span></code></a> instance;</p></li>
<li><p>‘handle’ (optional): <a class="reference internal" href="#asyncio.Handle" title="asyncio.Handle"><code class="xref py py-class docutils literal notranslate"><span class="pre">asyncio.Handle</span></code></a> instance;</p></li>
<li><p>‘protocol’ (optional): <a class="reference internal" href="asyncio-protocol.html#asyncio-protocol"><span class="std std-ref">Protocol</span></a> instance;</p></li>
<li><p>‘transport’ (optional): <a class="reference internal" href="asyncio-protocol.html#asyncio-transport"><span class="std std-ref">Transport</span></a> instance;</p></li>
<li><p>‘socket’ (optional): <a class="reference internal" href="socket.html#socket.socket" title="socket.socket"><code class="xref py py-class docutils literal notranslate"><span class="pre">socket.socket</span></code></a> instance;</p></li>
<li><p>‘source_traceback’ (optional): Traceback of the source;</p></li>
<li><p>‘handle_traceback’ (optional): Traceback of the handle;</p></li>
<li><dl class="simple">
<dt>‘asyncgen’ (optional): Asynchronous generator that caused</dt><dd><p>the exception.</p>
</dd>
</dl>
</li>
</ul>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>This method should not be overloaded in subclassed
event loops. For custom exception handling, use
the <a class="reference internal" href="#asyncio.loop.set_exception_handler" title="asyncio.loop.set_exception_handler"><code class="xref py py-meth docutils literal notranslate"><span class="pre">set_exception_handler()</span></code></a> method.</p>
</div>
</dd></dl>
</section>
<section id="enabling-debug-mode">
<h3><a class="toc-backref" href="#id16" role="doc-backlink">Enabling debug mode</a><a class="headerlink" href="#enabling-debug-mode" title="Link to this heading">¶</a></h3>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.get_debug">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">get_debug</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.get_debug" title="Link to this definition">¶</a></dt>
<dd><p>Get the debug mode (<a class="reference internal" href="functions.html#bool" title="bool"><code class="xref py py-class docutils literal notranslate"><span class="pre">bool</span></code></a>) of the event loop.</p>
<p>The default value is <code class="docutils literal notranslate"><span class="pre">True</span></code> if the environment variable
<span class="target" id="index-5"></span><a class="reference internal" href="../using/cmdline.html#envvar-PYTHONASYNCIODEBUG"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONASYNCIODEBUG</span></code></a> is set to a non-empty string, <code class="docutils literal notranslate"><span class="pre">False</span></code>
otherwise.</p>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.set_debug">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">set_debug</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">enabled</span></span><span class="p"><span class="pre">:</span></span><span class="w"> </span><span class="n"><a class="reference internal" href="functions.html#bool" title="bool"><span class="pre">bool</span></a></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.set_debug" title="Link to this definition">¶</a></dt>
<dd><p>Set the debug mode of the event loop.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.7: </span>The new <a class="reference internal" href="devmode.html#devmode"><span class="std std-ref">Python Development Mode</span></a> can now also be used
to enable the debug mode.</p>
</div>
</dd></dl>
<dl class="py attribute">
<dt class="sig sig-object py" id="asyncio.loop.slow_callback_duration">
<span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">slow_callback_duration</span></span><a class="headerlink" href="#asyncio.loop.slow_callback_duration" title="Link to this definition">¶</a></dt>
<dd><p>This attribute can be used to set the
minimum execution duration in seconds that is considered “slow”.
When debug mode is enabled, “slow” callbacks are logged.</p>
<p>Default value is 100 milliseconds.</p>
</dd></dl>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<p>The <a class="reference internal" href="asyncio-dev.html#asyncio-debug-mode"><span class="std std-ref">debug mode of asyncio</span></a>.</p>
</div>
</section>
<section id="running-subprocesses">
<h3><a class="toc-backref" href="#id17" role="doc-backlink">Running Subprocesses</a><a class="headerlink" href="#running-subprocesses" title="Link to this heading">¶</a></h3>
<p>Methods described in this subsections are low-level. In regular
async/await code consider using the high-level
<a class="reference internal" href="asyncio-subprocess.html#asyncio.create_subprocess_shell" title="asyncio.create_subprocess_shell"><code class="xref py py-func docutils literal notranslate"><span class="pre">asyncio.create_subprocess_shell()</span></code></a> and
<a class="reference internal" href="asyncio-subprocess.html#asyncio.create_subprocess_exec" title="asyncio.create_subprocess_exec"><code class="xref py py-func docutils literal notranslate"><span class="pre">asyncio.create_subprocess_exec()</span></code></a> convenience functions instead.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>On Windows, the default event loop <a class="reference internal" href="#asyncio.ProactorEventLoop" title="asyncio.ProactorEventLoop"><code class="xref py py-class docutils literal notranslate"><span class="pre">ProactorEventLoop</span></code></a> supports
subprocesses, whereas <a class="reference internal" href="#asyncio.SelectorEventLoop" title="asyncio.SelectorEventLoop"><code class="xref py py-class docutils literal notranslate"><span class="pre">SelectorEventLoop</span></code></a> does not. See
<a class="reference internal" href="asyncio-platforms.html#asyncio-windows-subprocess"><span class="std std-ref">Subprocess Support on Windows</span></a> for
details.</p>
</div>
<dl class="py method" id="loop-subprocess-exec">
<dt class="sig sig-object py" id="asyncio.loop.subprocess_exec">
<em class="property"><span class="k"><span class="pre">async</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">subprocess_exec</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">protocol_factory</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">*</span></span><span class="n"><span class="pre">args</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">stdin</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">subprocess.PIPE</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">stdout</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">subprocess.PIPE</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">stderr</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">subprocess.PIPE</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">**</span></span><span class="n"><span class="pre">kwargs</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.subprocess_exec" title="Link to this definition">¶</a></dt>
<dd><p>Create a subprocess from one or more string arguments specified by
<em>args</em>.</p>
<p><em>args</em> must be a list of strings represented by:</p>
<ul class="simple">
<li><p><a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a>;</p></li>
<li><p>or <a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a>, encoded to the
<a class="reference internal" href="os.html#filesystem-encoding"><span class="std std-ref">filesystem encoding</span></a>.</p></li>
</ul>
<p>The first string specifies the program executable,
and the remaining strings specify the arguments. Together, string
arguments form the <code class="docutils literal notranslate"><span class="pre">argv</span></code> of the program.</p>
<p>This is similar to the standard library <a class="reference internal" href="subprocess.html#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">subprocess.Popen</span></code></a>
class called with <code class="docutils literal notranslate"><span class="pre">shell=False</span></code> and the list of strings passed as
the first argument; however, where <code class="xref py py-class docutils literal notranslate"><span class="pre">Popen</span></code> takes
a single argument which is list of strings, <em>subprocess_exec</em>
takes multiple string arguments.</p>
<p>The <em>protocol_factory</em> must be a callable returning a subclass of the
<a class="reference internal" href="asyncio-protocol.html#asyncio.SubprocessProtocol" title="asyncio.SubprocessProtocol"><code class="xref py py-class docutils literal notranslate"><span class="pre">asyncio.SubprocessProtocol</span></code></a> class.</p>
<p>Other parameters:</p>
<ul>
<li><p><em>stdin</em> can be any of these:</p>
<ul class="simple">
<li><p>a file-like object</p></li>
<li><p>an existing file descriptor (a positive integer), for example those created with <a class="reference internal" href="os.html#os.pipe" title="os.pipe"><code class="xref py py-meth docutils literal notranslate"><span class="pre">os.pipe()</span></code></a></p></li>
<li><p>the <a class="reference internal" href="subprocess.html#subprocess.PIPE" title="subprocess.PIPE"><code class="xref py py-const docutils literal notranslate"><span class="pre">subprocess.PIPE</span></code></a> constant (default) which will create a new
pipe and connect it,</p></li>
<li><p>the value <code class="docutils literal notranslate"><span class="pre">None</span></code> which will make the subprocess inherit the file
descriptor from this process</p></li>
<li><p>the <a class="reference internal" href="subprocess.html#subprocess.DEVNULL" title="subprocess.DEVNULL"><code class="xref py py-const docutils literal notranslate"><span class="pre">subprocess.DEVNULL</span></code></a> constant which indicates that the
special <a class="reference internal" href="os.html#os.devnull" title="os.devnull"><code class="xref py py-data docutils literal notranslate"><span class="pre">os.devnull</span></code></a> file will be used</p></li>
</ul>
</li>
<li><p><em>stdout</em> can be any of these:</p>
<ul class="simple">
<li><p>a file-like object</p></li>
<li><p>the <a class="reference internal" href="subprocess.html#subprocess.PIPE" title="subprocess.PIPE"><code class="xref py py-const docutils literal notranslate"><span class="pre">subprocess.PIPE</span></code></a> constant (default) which will create a new
pipe and connect it,</p></li>
<li><p>the value <code class="docutils literal notranslate"><span class="pre">None</span></code> which will make the subprocess inherit the file
descriptor from this process</p></li>
<li><p>the <a class="reference internal" href="subprocess.html#subprocess.DEVNULL" title="subprocess.DEVNULL"><code class="xref py py-const docutils literal notranslate"><span class="pre">subprocess.DEVNULL</span></code></a> constant which indicates that the
special <a class="reference internal" href="os.html#os.devnull" title="os.devnull"><code class="xref py py-data docutils literal notranslate"><span class="pre">os.devnull</span></code></a> file will be used</p></li>
</ul>
</li>
<li><p><em>stderr</em> can be any of these:</p>
<ul class="simple">
<li><p>a file-like object</p></li>
<li><p>the <a class="reference internal" href="subprocess.html#subprocess.PIPE" title="subprocess.PIPE"><code class="xref py py-const docutils literal notranslate"><span class="pre">subprocess.PIPE</span></code></a> constant (default) which will create a new
pipe and connect it,</p></li>
<li><p>the value <code class="docutils literal notranslate"><span class="pre">None</span></code> which will make the subprocess inherit the file
descriptor from this process</p></li>
<li><p>the <a class="reference internal" href="subprocess.html#subprocess.DEVNULL" title="subprocess.DEVNULL"><code class="xref py py-const docutils literal notranslate"><span class="pre">subprocess.DEVNULL</span></code></a> constant which indicates that the
special <a class="reference internal" href="os.html#os.devnull" title="os.devnull"><code class="xref py py-data docutils literal notranslate"><span class="pre">os.devnull</span></code></a> file will be used</p></li>
<li><p>the <a class="reference internal" href="subprocess.html#subprocess.STDOUT" title="subprocess.STDOUT"><code class="xref py py-const docutils literal notranslate"><span class="pre">subprocess.STDOUT</span></code></a> constant which will connect the standard
error stream to the process’ standard output stream</p></li>
</ul>
</li>
<li><p>All other keyword arguments are passed to <a class="reference internal" href="subprocess.html#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">subprocess.Popen</span></code></a>
without interpretation, except for <em>bufsize</em>, <em>universal_newlines</em>,
<em>shell</em>, <em>text</em>, <em>encoding</em> and <em>errors</em>, which should not be specified
at all.</p>
<p>The <code class="docutils literal notranslate"><span class="pre">asyncio</span></code> subprocess API does not support decoding the streams
as text. <a class="reference internal" href="stdtypes.html#bytes.decode" title="bytes.decode"><code class="xref py py-func docutils literal notranslate"><span class="pre">bytes.decode()</span></code></a> can be used to convert the bytes returned
from the stream to text.</p>
</li>
</ul>
<p>If a file-like object passed as <em>stdin</em>, <em>stdout</em> or <em>stderr</em> represents a
pipe, then the other side of this pipe should be registered with
<a class="reference internal" href="#asyncio.loop.connect_write_pipe" title="asyncio.loop.connect_write_pipe"><code class="xref py py-meth docutils literal notranslate"><span class="pre">connect_write_pipe()</span></code></a> or <a class="reference internal" href="#asyncio.loop.connect_read_pipe" title="asyncio.loop.connect_read_pipe"><code class="xref py py-meth docutils literal notranslate"><span class="pre">connect_read_pipe()</span></code></a> for use
with the event loop.</p>
<p>See the constructor of the <a class="reference internal" href="subprocess.html#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">subprocess.Popen</span></code></a> class
for documentation on other arguments.</p>
<p>Returns a pair of <code class="docutils literal notranslate"><span class="pre">(transport,</span> <span class="pre">protocol)</span></code>, where <em>transport</em>
conforms to the <a class="reference internal" href="asyncio-protocol.html#asyncio.SubprocessTransport" title="asyncio.SubprocessTransport"><code class="xref py py-class docutils literal notranslate"><span class="pre">asyncio.SubprocessTransport</span></code></a> base class and
<em>protocol</em> is an object instantiated by the <em>protocol_factory</em>.</p>
<p>If the transport is closed or is garbage collected, the child process
is killed if it is still running.</p>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.loop.subprocess_shell">
<em class="property"><span class="k"><span class="pre">async</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">loop.</span></span><span class="sig-name descname"><span class="pre">subprocess_shell</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">protocol_factory</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">cmd</span></span></em>, <em class="sig-param"><span class="keyword-only-separator o"><abbr title="Keyword-only parameters separator (PEP 3102)"><span class="pre">*</span></abbr></span></em>, <em class="sig-param"><span class="n"><span class="pre">stdin</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">subprocess.PIPE</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">stdout</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">subprocess.PIPE</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">stderr</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">subprocess.PIPE</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">**</span></span><span class="n"><span class="pre">kwargs</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.loop.subprocess_shell" title="Link to this definition">¶</a></dt>
<dd><p>Create a subprocess from <em>cmd</em>, which can be a <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a> or a
<a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> string encoded to the
<a class="reference internal" href="os.html#filesystem-encoding"><span class="std std-ref">filesystem encoding</span></a>,
using the platform’s “shell” syntax.</p>
<p>This is similar to the standard library <a class="reference internal" href="subprocess.html#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">subprocess.Popen</span></code></a>
class called with <code class="docutils literal notranslate"><span class="pre">shell=True</span></code>.</p>
<p>The <em>protocol_factory</em> must be a callable returning a subclass of the
<a class="reference internal" href="asyncio-protocol.html#asyncio.SubprocessProtocol" title="asyncio.SubprocessProtocol"><code class="xref py py-class docutils literal notranslate"><span class="pre">SubprocessProtocol</span></code></a> class.</p>
<p>See <a class="reference internal" href="#asyncio.loop.subprocess_exec" title="asyncio.loop.subprocess_exec"><code class="xref py py-meth docutils literal notranslate"><span class="pre">subprocess_exec()</span></code></a> for more details about
the remaining arguments.</p>
<p>Returns a pair of <code class="docutils literal notranslate"><span class="pre">(transport,</span> <span class="pre">protocol)</span></code>, where <em>transport</em>
conforms to the <a class="reference internal" href="asyncio-protocol.html#asyncio.SubprocessTransport" title="asyncio.SubprocessTransport"><code class="xref py py-class docutils literal notranslate"><span class="pre">SubprocessTransport</span></code></a> base class and
<em>protocol</em> is an object instantiated by the <em>protocol_factory</em>.</p>
<p>If the transport is closed or is garbage collected, the child process
is killed if it is still running.</p>
</dd></dl>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>It is the application’s responsibility to ensure that all whitespace
and special characters are quoted appropriately to avoid <a class="reference external" href="https://en.wikipedia.org/wiki/Shell_injection#Shell_injection">shell injection</a>
vulnerabilities. The <a class="reference internal" href="shlex.html#shlex.quote" title="shlex.quote"><code class="xref py py-func docutils literal notranslate"><span class="pre">shlex.quote()</span></code></a> function can be used to
properly escape whitespace and special characters in strings that
are going to be used to construct shell commands.</p>
</div>
</section>
</section>
<section id="callback-handles">
<h2>Callback Handles<a class="headerlink" href="#callback-handles" title="Link to this heading">¶</a></h2>
<dl class="py class">
<dt class="sig sig-object py" id="asyncio.Handle">
<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">Handle</span></span><a class="headerlink" href="#asyncio.Handle" title="Link to this definition">¶</a></dt>
<dd><p>A callback wrapper object returned by <a class="reference internal" href="#asyncio.loop.call_soon" title="asyncio.loop.call_soon"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.call_soon()</span></code></a>,
<a class="reference internal" href="#asyncio.loop.call_soon_threadsafe" title="asyncio.loop.call_soon_threadsafe"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.call_soon_threadsafe()</span></code></a>.</p>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.Handle.get_context">
<span class="sig-name descname"><span class="pre">get_context</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.Handle.get_context" title="Link to this definition">¶</a></dt>
<dd><p>Return the <a class="reference internal" href="contextvars.html#contextvars.Context" title="contextvars.Context"><code class="xref py py-class docutils literal notranslate"><span class="pre">contextvars.Context</span></code></a> object
associated with the handle.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.12.</span></p>
</div>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.Handle.cancel">
<span class="sig-name descname"><span class="pre">cancel</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.Handle.cancel" title="Link to this definition">¶</a></dt>
<dd><p>Cancel the callback. If the callback has already been canceled
or executed, this method has no effect.</p>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.Handle.cancelled">
<span class="sig-name descname"><span class="pre">cancelled</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.Handle.cancelled" title="Link to this definition">¶</a></dt>
<dd><p>Return <code class="docutils literal notranslate"><span class="pre">True</span></code> if the callback was cancelled.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.7.</span></p>
</div>
</dd></dl>
</dd></dl>
<dl class="py class">
<dt class="sig sig-object py" id="asyncio.TimerHandle">
<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">TimerHandle</span></span><a class="headerlink" href="#asyncio.TimerHandle" title="Link to this definition">¶</a></dt>
<dd><p>A callback wrapper object returned by <a class="reference internal" href="#asyncio.loop.call_later" title="asyncio.loop.call_later"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.call_later()</span></code></a>,
and <a class="reference internal" href="#asyncio.loop.call_at" title="asyncio.loop.call_at"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.call_at()</span></code></a>.</p>
<p>This class is a subclass of <a class="reference internal" href="#asyncio.Handle" title="asyncio.Handle"><code class="xref py py-class docutils literal notranslate"><span class="pre">Handle</span></code></a>.</p>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.TimerHandle.when">
<span class="sig-name descname"><span class="pre">when</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.TimerHandle.when" title="Link to this definition">¶</a></dt>
<dd><p>Return a scheduled callback time as <a class="reference internal" href="functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate"><span class="pre">float</span></code></a> seconds.</p>
<p>The time is an absolute timestamp, using the same time
reference as <a class="reference internal" href="#asyncio.loop.time" title="asyncio.loop.time"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.time()</span></code></a>.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.7.</span></p>
</div>
</dd></dl>
</dd></dl>
</section>
<section id="server-objects">
<h2>Server Objects<a class="headerlink" href="#server-objects" title="Link to this heading">¶</a></h2>
<p>Server objects are created by <a class="reference internal" href="#asyncio.loop.create_server" title="asyncio.loop.create_server"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_server()</span></code></a>,
<a class="reference internal" href="#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>, <a class="reference internal" href="asyncio-stream.html#asyncio.start_server" title="asyncio.start_server"><code class="xref py py-func docutils literal notranslate"><span class="pre">start_server()</span></code></a>,
and <a class="reference internal" href="asyncio-stream.html#asyncio.start_unix_server" title="asyncio.start_unix_server"><code class="xref py py-func docutils literal notranslate"><span class="pre">start_unix_server()</span></code></a> functions.</p>
<p>Do not instantiate the <a class="reference internal" href="#asyncio.Server" title="asyncio.Server"><code class="xref py py-class docutils literal notranslate"><span class="pre">Server</span></code></a> class directly.</p>
<dl class="py class">
<dt class="sig sig-object py" id="asyncio.Server">
<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">Server</span></span><a class="headerlink" href="#asyncio.Server" title="Link to this definition">¶</a></dt>
<dd><p><em>Server</em> objects are asynchronous context managers. When used in an
<code class="docutils literal notranslate"><span class="pre">async</span> <span class="pre">with</span></code> statement, it’s guaranteed that the Server object is
closed and not accepting new connections when the <code class="docutils literal notranslate"><span class="pre">async</span> <span class="pre">with</span></code>
statement is completed:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">srv</span> <span class="o">=</span> <span class="k">await</span> <span class="n">loop</span><span class="o">.</span><span class="n">create_server</span><span class="p">(</span><span class="o">...</span><span class="p">)</span>
<span class="k">async</span> <span class="k">with</span> <span class="n">srv</span><span class="p">:</span>
<span class="c1"># some code</span>
<span class="c1"># At this point, srv is closed and no longer accepts new connections.</span>
</pre></div>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.7: </span>Server object is an asynchronous context manager since Python 3.7.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.11: </span>This class was exposed publicly as <code class="docutils literal notranslate"><span class="pre">asyncio.Server</span></code> in Python 3.9.11, 3.10.3 and 3.11.</p>
</div>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.Server.close">
<span class="sig-name descname"><span class="pre">close</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.Server.close" title="Link to this definition">¶</a></dt>
<dd><p>Stop serving: close listening sockets and set the <a class="reference internal" href="#asyncio.Server.sockets" title="asyncio.Server.sockets"><code class="xref py py-attr docutils literal notranslate"><span class="pre">sockets</span></code></a>
attribute to <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p>
<p>The sockets that represent existing incoming client connections
are left open.</p>
<p>The server is closed asynchronously; use the <a class="reference internal" href="#asyncio.Server.wait_closed" title="asyncio.Server.wait_closed"><code class="xref py py-meth docutils literal notranslate"><span class="pre">wait_closed()</span></code></a>
coroutine to wait until the server is closed (and no more
connections are active).</p>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.Server.close_clients">
<span class="sig-name descname"><span class="pre">close_clients</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.Server.close_clients" title="Link to this definition">¶</a></dt>
<dd><p>Close all existing incoming client connections.</p>
<p>Calls <a class="reference internal" href="asyncio-protocol.html#asyncio.BaseTransport.close" title="asyncio.BaseTransport.close"><code class="xref py py-meth docutils literal notranslate"><span class="pre">close()</span></code></a> on all associated
transports.</p>
<p><a class="reference internal" href="#asyncio.Server.close" title="asyncio.Server.close"><code class="xref py py-meth docutils literal notranslate"><span class="pre">close()</span></code></a> should be called before <code class="xref py py-meth docutils literal notranslate"><span class="pre">close_clients()</span></code> when
closing the server to avoid races with new clients connecting.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.13.</span></p>
</div>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.Server.abort_clients">
<span class="sig-name descname"><span class="pre">abort_clients</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.Server.abort_clients" title="Link to this definition">¶</a></dt>
<dd><p>Close all existing incoming client connections immediately,
without waiting for pending operations to complete.</p>
<p>Calls <a class="reference internal" href="asyncio-protocol.html#asyncio.WriteTransport.abort" title="asyncio.WriteTransport.abort"><code class="xref py py-meth docutils literal notranslate"><span class="pre">abort()</span></code></a> on all associated
transports.</p>
<p><a class="reference internal" href="#asyncio.Server.close" title="asyncio.Server.close"><code class="xref py py-meth docutils literal notranslate"><span class="pre">close()</span></code></a> should be called before <code class="xref py py-meth docutils literal notranslate"><span class="pre">abort_clients()</span></code> when
closing the server to avoid races with new clients connecting.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.13.</span></p>
</div>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.Server.get_loop">
<span class="sig-name descname"><span class="pre">get_loop</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.Server.get_loop" title="Link to this definition">¶</a></dt>
<dd><p>Return the event loop associated with the server object.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.7.</span></p>
</div>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.Server.start_serving">
<em class="property"><span class="k"><span class="pre">async</span></span><span class="w"> </span></em><span class="sig-name descname"><span class="pre">start_serving</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.Server.start_serving" title="Link to this definition">¶</a></dt>
<dd><p>Start accepting connections.</p>
<p>This method is idempotent, so it can be called when
the server is already serving.</p>
<p>The <em>start_serving</em> keyword-only parameter to
<a class="reference internal" href="#asyncio.loop.create_server" title="asyncio.loop.create_server"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_server()</span></code></a> and
<a class="reference internal" href="asyncio-stream.html#asyncio.start_server" title="asyncio.start_server"><code class="xref py py-meth docutils literal notranslate"><span class="pre">asyncio.start_server()</span></code></a> allows creating a Server object
that is not accepting connections initially. In this case
<code class="docutils literal notranslate"><span class="pre">Server.start_serving()</span></code>, or <a class="reference internal" href="#asyncio.Server.serve_forever" title="asyncio.Server.serve_forever"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Server.serve_forever()</span></code></a> can be used
to make the Server start accepting connections.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.7.</span></p>
</div>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.Server.serve_forever">
<em class="property"><span class="k"><span class="pre">async</span></span><span class="w"> </span></em><span class="sig-name descname"><span class="pre">serve_forever</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.Server.serve_forever" title="Link to this definition">¶</a></dt>
<dd><p>Start accepting connections until the coroutine is cancelled.
Cancellation of <code class="docutils literal notranslate"><span class="pre">serve_forever</span></code> task causes the server
to be closed.</p>
<p>This method can be called if the server is already accepting
connections. Only one <code class="docutils literal notranslate"><span class="pre">serve_forever</span></code> task can exist per
one <em>Server</em> object.</p>
<p>Example:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">client_connected</span><span class="p">(</span><span class="n">reader</span><span class="p">,</span> <span class="n">writer</span><span class="p">):</span>
<span class="c1"># Communicate with the client with</span>
<span class="c1"># reader/writer streams. For example:</span>
<span class="k">await</span> <span class="n">reader</span><span class="o">.</span><span class="n">readline</span><span class="p">()</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="n">host</span><span class="p">,</span> <span class="n">port</span><span class="p">):</span>
<span class="n">srv</span> <span class="o">=</span> <span class="k">await</span> <span class="n">asyncio</span><span class="o">.</span><span class="n">start_server</span><span class="p">(</span>
<span class="n">client_connected</span><span class="p">,</span> <span class="n">host</span><span class="p">,</span> <span class="n">port</span><span class="p">)</span>
<span class="k">await</span> <span class="n">srv</span><span class="o">.</span><span class="n">serve_forever</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><span class="s1">'127.0.0.1'</span><span class="p">,</span> <span class="mi">0</span><span class="p">))</span>
</pre></div>
</div>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.7.</span></p>
</div>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.Server.is_serving">
<span class="sig-name descname"><span class="pre">is_serving</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.Server.is_serving" title="Link to this definition">¶</a></dt>
<dd><p>Return <code class="docutils literal notranslate"><span class="pre">True</span></code> if the server is accepting new connections.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.7.</span></p>
</div>
</dd></dl>
<dl class="py method">
<dt class="sig sig-object py" id="asyncio.Server.wait_closed">
<em class="property"><span class="k"><span class="pre">async</span></span><span class="w"> </span></em><span class="sig-name descname"><span class="pre">wait_closed</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.Server.wait_closed" title="Link to this definition">¶</a></dt>
<dd><p>Wait until the <a class="reference internal" href="#asyncio.Server.close" title="asyncio.Server.close"><code class="xref py py-meth docutils literal notranslate"><span class="pre">close()</span></code></a> method completes and all active
connections have finished.</p>
</dd></dl>
<dl class="py attribute">
<dt class="sig sig-object py" id="asyncio.Server.sockets">
<span class="sig-name descname"><span class="pre">sockets</span></span><a class="headerlink" href="#asyncio.Server.sockets" title="Link to this definition">¶</a></dt>
<dd><p>List of socket-like objects, <code class="docutils literal notranslate"><span class="pre">asyncio.trsock.TransportSocket</span></code>, which
the server is listening on.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.7: </span>Prior to Python 3.7 <code class="docutils literal notranslate"><span class="pre">Server.sockets</span></code> used to return an
internal list of server sockets directly. In 3.7 a copy
of that list is returned.</p>
</div>
</dd></dl>
</dd></dl>
</section>
<section id="event-loop-implementations">
<span id="asyncio-event-loop-implementations"></span><span id="asyncio-event-loops"></span><h2>Event Loop Implementations<a class="headerlink" href="#event-loop-implementations" title="Link to this heading">¶</a></h2>
<p>asyncio ships with two different event loop implementations:
<a class="reference internal" href="#asyncio.SelectorEventLoop" title="asyncio.SelectorEventLoop"><code class="xref py py-class docutils literal notranslate"><span class="pre">SelectorEventLoop</span></code></a> and <a class="reference internal" href="#asyncio.ProactorEventLoop" title="asyncio.ProactorEventLoop"><code class="xref py py-class docutils literal notranslate"><span class="pre">ProactorEventLoop</span></code></a>.</p>
<p>By default asyncio is configured to use <a class="reference internal" href="#asyncio.EventLoop" title="asyncio.EventLoop"><code class="xref py py-class docutils literal notranslate"><span class="pre">EventLoop</span></code></a>.</p>
<dl class="py class">
<dt class="sig sig-object py" id="asyncio.SelectorEventLoop">
<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">SelectorEventLoop</span></span><a class="headerlink" href="#asyncio.SelectorEventLoop" title="Link to this definition">¶</a></dt>
<dd><p>A subclass of <a class="reference internal" href="#asyncio.AbstractEventLoop" title="asyncio.AbstractEventLoop"><code class="xref py py-class docutils literal notranslate"><span class="pre">AbstractEventLoop</span></code></a> based on the
<a class="reference internal" href="selectors.html#module-selectors" title="selectors: High-level I/O multiplexing."><code class="xref py py-mod docutils literal notranslate"><span class="pre">selectors</span></code></a> module.</p>
<p>Uses the most efficient <em>selector</em> available for the given
platform. It is also possible to manually configure the
exact selector implementation to be used:</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="kn">import</span><span class="w"> </span><span class="nn">selectors</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="o">...</span>
<span class="n">loop_factory</span> <span class="o">=</span> <span class="k">lambda</span><span class="p">:</span> <span class="n">asyncio</span><span class="o">.</span><span class="n">SelectorEventLoop</span><span class="p">(</span><span class="n">selectors</span><span class="o">.</span><span class="n">SelectSelector</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> <span class="n">loop_factory</span><span class="o">=</span><span class="n">loop_factory</span><span class="p">)</span>
</pre></div>
</div>
<div class="availability docutils container">
<p><a class="reference internal" href="intro.html#availability"><span class="std std-ref">Availability</span></a>: Unix, Windows.</p>
</div>
</dd></dl>
<dl class="py class">
<dt class="sig sig-object py" id="asyncio.ProactorEventLoop">
<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">ProactorEventLoop</span></span><a class="headerlink" href="#asyncio.ProactorEventLoop" title="Link to this definition">¶</a></dt>
<dd><p>A subclass of <a class="reference internal" href="#asyncio.AbstractEventLoop" title="asyncio.AbstractEventLoop"><code class="xref py py-class docutils literal notranslate"><span class="pre">AbstractEventLoop</span></code></a> for Windows that uses “I/O Completion Ports” (IOCP).</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="admonition seealso">
<p class="admonition-title">See also</p>
<p><a class="reference external" href="https://learn.microsoft.com/windows/win32/fileio/i-o-completion-ports">MSDN documentation on I/O Completion Ports</a>.</p>
</div>
</dd></dl>
<dl class="py class">
<dt class="sig sig-object py" id="asyncio.EventLoop">
<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">EventLoop</span></span><a class="headerlink" href="#asyncio.EventLoop" title="Link to this definition">¶</a></dt>
<dd><blockquote>
<div><p>An alias to the most efficient available subclass of <a class="reference internal" href="#asyncio.AbstractEventLoop" title="asyncio.AbstractEventLoop"><code class="xref py py-class docutils literal notranslate"><span class="pre">AbstractEventLoop</span></code></a> for the given
platform.</p>
<p>It is an alias to <a class="reference internal" href="#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.ProactorEventLoop" title="asyncio.ProactorEventLoop"><code class="xref py py-class docutils literal notranslate"><span class="pre">ProactorEventLoop</span></code></a> on Windows.</p>
</div></blockquote>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.13.</span></p>
</div>
</dd></dl>
<dl class="py class">
<dt class="sig sig-object py" id="asyncio.AbstractEventLoop">
<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">AbstractEventLoop</span></span><a class="headerlink" href="#asyncio.AbstractEventLoop" title="Link to this definition">¶</a></dt>
<dd><p>Abstract base class for asyncio-compliant event loops.</p>
<p>The <a class="reference internal" href="#asyncio-event-loop-methods"><span class="std std-ref">Event Loop Methods</span></a> section lists all
methods that an alternative implementation of <code class="docutils literal notranslate"><span class="pre">AbstractEventLoop</span></code>
should have defined.</p>
</dd></dl>
</section>
<section id="examples">
<h2>Examples<a class="headerlink" href="#examples" title="Link to this heading">¶</a></h2>
<p>Note that all examples in this section <strong>purposefully</strong> show how
to use the low-level event loop APIs, such as <a class="reference internal" href="#asyncio.loop.run_forever" title="asyncio.loop.run_forever"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.run_forever()</span></code></a>
and <a class="reference internal" href="#asyncio.loop.call_soon" title="asyncio.loop.call_soon"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.call_soon()</span></code></a>. Modern asyncio applications rarely
need to be written this way; consider using the high-level functions
like <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>.</p>
<section id="hello-world-with-call-soon">
<span id="asyncio-example-lowlevel-helloworld"></span><h3>Hello World with call_soon()<a class="headerlink" href="#hello-world-with-call-soon" title="Link to this heading">¶</a></h3>
<p>An example using the <a class="reference internal" href="#asyncio.loop.call_soon" title="asyncio.loop.call_soon"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.call_soon()</span></code></a> method to schedule a
callback. The callback displays <code class="docutils literal notranslate"><span class="pre">"Hello</span> <span class="pre">World"</span></code> and then stops the
event loop:</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">def</span><span class="w"> </span><span class="nf">hello_world</span><span class="p">(</span><span class="n">loop</span><span class="p">):</span>
<span class="w"> </span><span class="sd">"""A callback to print 'Hello World' and stop the event loop"""</span>
<span class="nb">print</span><span class="p">(</span><span class="s1">'Hello World'</span><span class="p">)</span>
<span class="n">loop</span><span class="o">.</span><span class="n">stop</span><span class="p">()</span>
<span class="n">loop</span> <span class="o">=</span> <span class="n">asyncio</span><span class="o">.</span><span class="n">new_event_loop</span><span class="p">()</span>
<span class="c1"># Schedule a call to hello_world()</span>
<span class="n">loop</span><span class="o">.</span><span class="n">call_soon</span><span class="p">(</span><span class="n">hello_world</span><span class="p">,</span> <span class="n">loop</span><span class="p">)</span>
<span class="c1"># Blocking call interrupted by loop.stop()</span>
<span class="k">try</span><span class="p">:</span>
<span class="n">loop</span><span class="o">.</span><span class="n">run_forever</span><span class="p">()</span>
<span class="k">finally</span><span class="p">:</span>
<span class="n">loop</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
</pre></div>
</div>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<p>A similar <a class="reference internal" href="asyncio-task.html#coroutine"><span class="std std-ref">Hello World</span></a>
example created with a coroutine and 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">run()</span></code></a> function.</p>
</div>
</section>
<section id="display-the-current-date-with-call-later">
<span id="asyncio-example-call-later"></span><h3>Display the current date with call_later()<a class="headerlink" href="#display-the-current-date-with-call-later" title="Link to this heading">¶</a></h3>
<p>An example of a callback displaying the current date every second. The
callback uses the <a class="reference internal" href="#asyncio.loop.call_later" title="asyncio.loop.call_later"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.call_later()</span></code></a> method to reschedule itself
after 5 seconds, and then stops the event loop:</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="kn">import</span><span class="w"> </span><span class="nn">datetime</span>
<span class="k">def</span><span class="w"> </span><span class="nf">display_date</span><span class="p">(</span><span class="n">end_time</span><span class="p">,</span> <span class="n">loop</span><span class="p">):</span>
<span class="nb">print</span><span class="p">(</span><span class="n">datetime</span><span class="o">.</span><span class="n">datetime</span><span class="o">.</span><span class="n">now</span><span class="p">())</span>
<span class="k">if</span> <span class="p">(</span><span class="n">loop</span><span class="o">.</span><span class="n">time</span><span class="p">()</span> <span class="o">+</span> <span class="mf">1.0</span><span class="p">)</span> <span class="o"><</span> <span class="n">end_time</span><span class="p">:</span>
<span class="n">loop</span><span class="o">.</span><span class="n">call_later</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="n">display_date</span><span class="p">,</span> <span class="n">end_time</span><span class="p">,</span> <span class="n">loop</span><span class="p">)</span>
<span class="k">else</span><span class="p">:</span>
<span class="n">loop</span><span class="o">.</span><span class="n">stop</span><span class="p">()</span>
<span class="n">loop</span> <span class="o">=</span> <span class="n">asyncio</span><span class="o">.</span><span class="n">new_event_loop</span><span class="p">()</span>
<span class="c1"># Schedule the first call to display_date()</span>
<span class="n">end_time</span> <span class="o">=</span> <span class="n">loop</span><span class="o">.</span><span class="n">time</span><span class="p">()</span> <span class="o">+</span> <span class="mf">5.0</span>
<span class="n">loop</span><span class="o">.</span><span class="n">call_soon</span><span class="p">(</span><span class="n">display_date</span><span class="p">,</span> <span class="n">end_time</span><span class="p">,</span> <span class="n">loop</span><span class="p">)</span>
<span class="c1"># Blocking call interrupted by loop.stop()</span>
<span class="k">try</span><span class="p">:</span>
<span class="n">loop</span><span class="o">.</span><span class="n">run_forever</span><span class="p">()</span>
<span class="k">finally</span><span class="p">:</span>
<span class="n">loop</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
</pre></div>
</div>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<p>A similar <a class="reference internal" href="asyncio-task.html#asyncio-example-sleep"><span class="std std-ref">current date</span></a> example
created with a coroutine and 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">run()</span></code></a> function.</p>
</div>
</section>
<section id="watch-a-file-descriptor-for-read-events">
<span id="asyncio-example-watch-fd"></span><h3>Watch a file descriptor for read events<a class="headerlink" href="#watch-a-file-descriptor-for-read-events" title="Link to this heading">¶</a></h3>
<p>Wait until a file descriptor received some data using the
<a class="reference internal" href="#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> method and then close the event loop:</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="kn">from</span><span class="w"> </span><span class="nn">socket</span><span class="w"> </span><span class="kn">import</span> <span class="n">socketpair</span>
<span class="c1"># Create a pair of connected file descriptors</span>
<span class="n">rsock</span><span class="p">,</span> <span class="n">wsock</span> <span class="o">=</span> <span class="n">socketpair</span><span class="p">()</span>
<span class="n">loop</span> <span class="o">=</span> <span class="n">asyncio</span><span class="o">.</span><span class="n">new_event_loop</span><span class="p">()</span>
<span class="k">def</span><span class="w"> </span><span class="nf">reader</span><span class="p">():</span>
<span class="n">data</span> <span class="o">=</span> <span class="n">rsock</span><span class="o">.</span><span class="n">recv</span><span class="p">(</span><span class="mi">100</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="s2">"Received:"</span><span class="p">,</span> <span class="n">data</span><span class="o">.</span><span class="n">decode</span><span class="p">())</span>
<span class="c1"># We are done: unregister the file descriptor</span>
<span class="n">loop</span><span class="o">.</span><span class="n">remove_reader</span><span class="p">(</span><span class="n">rsock</span><span class="p">)</span>
<span class="c1"># Stop the event loop</span>
<span class="n">loop</span><span class="o">.</span><span class="n">stop</span><span class="p">()</span>
<span class="c1"># Register the file descriptor for read event</span>
<span class="n">loop</span><span class="o">.</span><span class="n">add_reader</span><span class="p">(</span><span class="n">rsock</span><span class="p">,</span> <span class="n">reader</span><span class="p">)</span>
<span class="c1"># Simulate the reception of data from the network</span>
<span class="n">loop</span><span class="o">.</span><span class="n">call_soon</span><span class="p">(</span><span class="n">wsock</span><span class="o">.</span><span class="n">send</span><span class="p">,</span> <span class="s1">'abc'</span><span class="o">.</span><span class="n">encode</span><span class="p">())</span>
<span class="k">try</span><span class="p">:</span>
<span class="c1"># Run the event loop</span>
<span class="n">loop</span><span class="o">.</span><span class="n">run_forever</span><span class="p">()</span>
<span class="k">finally</span><span class="p">:</span>
<span class="c1"># We are done. Close sockets and the event loop.</span>
<span class="n">rsock</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
<span class="n">wsock</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
<span class="n">loop</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
</pre></div>
</div>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<ul class="simple">
<li><p>A similar <a class="reference internal" href="asyncio-protocol.html#asyncio-example-create-connection"><span class="std std-ref">example</span></a>
using transports, protocols, and the
<a class="reference internal" href="#asyncio.loop.create_connection" title="asyncio.loop.create_connection"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_connection()</span></code></a> method.</p></li>
<li><p>Another similar <a class="reference internal" href="asyncio-stream.html#asyncio-example-create-connection-streams"><span class="std std-ref">example</span></a>
using the high-level <a class="reference internal" href="asyncio-stream.html#asyncio.open_connection" title="asyncio.open_connection"><code class="xref py py-func docutils literal notranslate"><span class="pre">asyncio.open_connection()</span></code></a> function
and streams.</p></li>
</ul>
</div>
</section>
<section id="set-signal-handlers-for-sigint-and-sigterm">
<span id="asyncio-example-unix-signals"></span><h3>Set signal handlers for SIGINT and SIGTERM<a class="headerlink" href="#set-signal-handlers-for-sigint-and-sigterm" title="Link to this heading">¶</a></h3>
<p>(This <code class="docutils literal notranslate"><span class="pre">signals</span></code> example only works on Unix.)</p>
<p>Register handlers for signals <a class="reference internal" href="signal.html#signal.SIGINT" title="signal.SIGINT"><code class="xref py py-const docutils literal notranslate"><span class="pre">SIGINT</span></code></a> and <a class="reference internal" href="signal.html#signal.SIGTERM" title="signal.SIGTERM"><code class="xref py py-const docutils literal notranslate"><span class="pre">SIGTERM</span></code></a>
using the <a class="reference internal" href="#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> method:</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="kn">import</span><span class="w"> </span><span class="nn">functools</span>
<span class="kn">import</span><span class="w"> </span><span class="nn">os</span>
<span class="kn">import</span><span class="w"> </span><span class="nn">signal</span>
<span class="k">def</span><span class="w"> </span><span class="nf">ask_exit</span><span class="p">(</span><span class="n">signame</span><span class="p">,</span> <span class="n">loop</span><span class="p">):</span>
<span class="nb">print</span><span class="p">(</span><span class="s2">"got signal </span><span class="si">%s</span><span class="s2">: exit"</span> <span class="o">%</span> <span class="n">signame</span><span class="p">)</span>
<span class="n">loop</span><span class="o">.</span><span class="n">stop</span><span class="p">()</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="n">loop</span> <span class="o">=</span> <span class="n">asyncio</span><span class="o">.</span><span class="n">get_running_loop</span><span class="p">()</span>
<span class="k">for</span> <span class="n">signame</span> <span class="ow">in</span> <span class="p">{</span><span class="s1">'SIGINT'</span><span class="p">,</span> <span class="s1">'SIGTERM'</span><span class="p">}:</span>
<span class="n">loop</span><span class="o">.</span><span class="n">add_signal_handler</span><span class="p">(</span>
<span class="nb">getattr</span><span class="p">(</span><span class="n">signal</span><span class="p">,</span> <span class="n">signame</span><span class="p">),</span>
<span class="n">functools</span><span class="o">.</span><span class="n">partial</span><span class="p">(</span><span class="n">ask_exit</span><span class="p">,</span> <span class="n">signame</span><span class="p">,</span> <span class="n">loop</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">3600</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="s2">"Event loop running for 1 hour, press Ctrl+C to interrupt."</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s2">"pid </span><span class="si">{</span><span class="n">os</span><span class="o">.</span><span class="n">getpid</span><span class="p">()</span><span class="si">}</span><span class="s2">: send SIGINT or SIGTERM to exit."</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>
</section>
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<h3><a href="../contents.html">Table of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">Event Loop</a><ul>
<li><a class="reference internal" href="#event-loop-methods">Event Loop Methods</a><ul>
<li><a class="reference internal" href="#running-and-stopping-the-loop">Running and stopping the loop</a></li>
<li><a class="reference internal" href="#scheduling-callbacks">Scheduling callbacks</a></li>
<li><a class="reference internal" href="#scheduling-delayed-callbacks">Scheduling delayed callbacks</a></li>
<li><a class="reference internal" href="#creating-futures-and-tasks">Creating Futures and Tasks</a></li>
<li><a class="reference internal" href="#opening-network-connections">Opening network connections</a></li>
<li><a class="reference internal" href="#creating-network-servers">Creating network servers</a></li>
<li><a class="reference internal" href="#transferring-files">Transferring files</a></li>
<li><a class="reference internal" href="#tls-upgrade">TLS Upgrade</a></li>
<li><a class="reference internal" href="#watching-file-descriptors">Watching file descriptors</a></li>
<li><a class="reference internal" href="#working-with-socket-objects-directly">Working with socket objects directly</a></li>
<li><a class="reference internal" href="#dns">DNS</a></li>
<li><a class="reference internal" href="#working-with-pipes">Working with pipes</a></li>
<li><a class="reference internal" href="#unix-signals">Unix signals</a></li>
<li><a class="reference internal" href="#executing-code-in-thread-or-process-pools">Executing code in thread or process pools</a></li>
<li><a class="reference internal" href="#error-handling-api">Error Handling API</a></li>
<li><a class="reference internal" href="#enabling-debug-mode">Enabling debug mode</a></li>
<li><a class="reference internal" href="#running-subprocesses">Running Subprocesses</a></li>
</ul>
</li>
<li><a class="reference internal" href="#callback-handles">Callback Handles</a></li>
<li><a class="reference internal" href="#server-objects">Server Objects</a></li>
<li><a class="reference internal" href="#event-loop-implementations">Event Loop Implementations</a></li>
<li><a class="reference internal" href="#examples">Examples</a><ul>
<li><a class="reference internal" href="#hello-world-with-call-soon">Hello World with call_soon()</a></li>
<li><a class="reference internal" href="#display-the-current-date-with-call-later">Display the current date with call_later()</a></li>
<li><a class="reference internal" href="#watch-a-file-descriptor-for-read-events">Watch a file descriptor for read events</a></li>
<li><a class="reference internal" href="#set-signal-handlers-for-sigint-and-sigterm">Set signal handlers for SIGINT and SIGTERM</a></li>
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