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<div class="section" id="module-sched">
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<span id="sched-event-scheduler"></span><h1>17.6. <a class="reference internal" href="#module-sched" title="sched: General purpose event scheduler."><code class="xref py py-mod docutils literal"><span class="pre">sched</span></code></a> — Event scheduler<a class="headerlink" href="#module-sched" title="Permalink to this headline">¶</a></h1>
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<p><strong>Source code:</strong> <a class="reference external" href="https://hg.python.org/cpython/file/3.5/Lib/sched.py">Lib/sched.py</a></p>
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<hr class="docutils" id="index-0" />
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<p>The <a class="reference internal" href="#module-sched" title="sched: General purpose event scheduler."><code class="xref py py-mod docutils literal"><span class="pre">sched</span></code></a> module defines a class which implements a general purpose event
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<dt id="sched.scheduler">
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<em class="property">class </em><code class="descclassname">sched.</code><code class="descname">scheduler</code><span class="sig-paren">(</span><em>timefunc=time.monotonic</em>, <em>delayfunc=time.sleep</em><span class="sig-paren">)</span><a class="headerlink" href="#sched.scheduler" title="Permalink to this definition">¶</a></dt>
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<dd><p>The <a class="reference internal" href="#sched.scheduler" title="sched.scheduler"><code class="xref py py-class docutils literal"><span class="pre">scheduler</span></code></a> class defines a generic interface to scheduling events.
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It needs two functions to actually deal with the “outside world” — <em>timefunc</em>
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should be callable without arguments, and return a number (the “time”, in any
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units whatsoever). If time.monotonic is not available, the <em>timefunc</em> default
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is time.time instead. The <em>delayfunc</em> function should be callable with one
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argument, compatible with the output of <em>timefunc</em>, and should delay that many
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time units. <em>delayfunc</em> will also be called with the argument <code class="docutils literal"><span class="pre">0</span></code> after each
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event is run to allow other threads an opportunity to run in multi-threaded
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<div class="versionchanged">
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<p><span class="versionmodified">Changed in version 3.3: </span><em>timefunc</em> and <em>delayfunc</em> parameters are optional.</p>
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<div class="versionchanged">
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<p><span class="versionmodified">Changed in version 3.3: </span><a class="reference internal" href="#sched.scheduler" title="sched.scheduler"><code class="xref py py-class docutils literal"><span class="pre">scheduler</span></code></a> class can be safely used in multi-threaded
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<div class="highlight-python3"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">sched</span><span class="o">,</span> <span class="nn">time</span>
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<span class="gp">>>> </span><span class="n">s</span> <span class="o">=</span> <span class="n">sched</span><span class="o">.</span><span class="n">scheduler</span><span class="p">(</span><span class="n">time</span><span class="o">.</span><span class="n">time</span><span class="p">,</span> <span class="n">time</span><span class="o">.</span><span class="n">sleep</span><span class="p">)</span>
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<span class="gp">>>> </span><span class="k">def</span> <span class="nf">print_time</span><span class="p">(</span><span class="n">a</span><span class="o">=</span><span class="s1">'default'</span><span class="p">):</span>
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<span class="gp">... </span> <span class="nb">print</span><span class="p">(</span><span class="s2">"From print_time"</span><span class="p">,</span> <span class="n">time</span><span class="o">.</span><span class="n">time</span><span class="p">(),</span> <span class="n">a</span><span class="p">)</span>
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<span class="gp">...</span>
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<span class="gp">>>> </span><span class="k">def</span> <span class="nf">print_some_times</span><span class="p">():</span>
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<span class="gp">... </span> <span class="nb">print</span><span class="p">(</span><span class="n">time</span><span class="o">.</span><span class="n">time</span><span class="p">())</span>
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<span class="gp">... </span> <span class="n">s</span><span class="o">.</span><span class="n">enter</span><span class="p">(</span><span class="mi">10</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="n">print_time</span><span class="p">)</span>
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<span class="gp">... </span> <span class="n">s</span><span class="o">.</span><span class="n">enter</span><span class="p">(</span><span class="mi">5</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="n">print_time</span><span class="p">,</span> <span class="n">argument</span><span class="o">=</span><span class="p">(</span><span class="s1">'positional'</span><span class="p">,))</span>
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<span class="gp">... </span> <span class="n">s</span><span class="o">.</span><span class="n">enter</span><span class="p">(</span><span class="mi">5</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="n">print_time</span><span class="p">,</span> <span class="n">kwargs</span><span class="o">=</span><span class="p">{</span><span class="s1">'a'</span><span class="p">:</span> <span class="s1">'keyword'</span><span class="p">})</span>
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<span class="gp">... </span> <span class="n">s</span><span class="o">.</span><span class="n">run</span><span class="p">()</span>
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<span class="gp">... </span> <span class="nb">print</span><span class="p">(</span><span class="n">time</span><span class="o">.</span><span class="n">time</span><span class="p">())</span>
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<span class="gp">...</span>
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<span class="gp">>>> </span><span class="n">print_some_times</span><span class="p">()</span>
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<span class="go">930343690.257</span>
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<span class="go">From print_time 930343695.274 positional</span>
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<span class="go">From print_time 930343695.275 keyword</span>
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<span class="go">From print_time 930343700.273 default</span>
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<span class="go">930343700.276</span>
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<div class="section" id="scheduler-objects">
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<span id="id1"></span><h2>17.6.1. Scheduler Objects<a class="headerlink" href="#scheduler-objects" title="Permalink to this headline">¶</a></h2>
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<p><a class="reference internal" href="#sched.scheduler" title="sched.scheduler"><code class="xref py py-class docutils literal"><span class="pre">scheduler</span></code></a> instances have the following methods and attributes:</p>
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<dt id="sched.scheduler.enterabs">
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<code class="descclassname">scheduler.</code><code class="descname">enterabs</code><span class="sig-paren">(</span><em>time</em>, <em>priority</em>, <em>action</em>, <em>argument=()</em>, <em>kwargs={}</em><span class="sig-paren">)</span><a class="headerlink" href="#sched.scheduler.enterabs" title="Permalink to this definition">¶</a></dt>
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<dd><p>Schedule a new event. The <em>time</em> argument should be a numeric type compatible
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with the return value of the <em>timefunc</em> function passed to the constructor.
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Events scheduled for the same <em>time</em> will be executed in the order of their
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<em>priority</em>.</p>
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<p>Executing the event means executing <code class="docutils literal"><span class="pre">action(*argument,</span> <span class="pre">**kwargs)</span></code>.
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<em>argument</em> is a sequence holding the positional arguments for <em>action</em>.
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<em>kwargs</em> is a dictionary holding the keyword arguments for <em>action</em>.</p>
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<p>Return value is an event which may be used for later cancellation of the event
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(see <a class="reference internal" href="#sched.scheduler.cancel" title="sched.scheduler.cancel"><code class="xref py py-meth docutils literal"><span class="pre">cancel()</span></code></a>).</p>
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<div class="versionchanged">
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<p><span class="versionmodified">Changed in version 3.3: </span><em>argument</em> parameter is optional.</p>
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<div class="versionadded">
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<p><span class="versionmodified">New in version 3.3: </span><em>kwargs</em> parameter was added.</p>
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<dt id="sched.scheduler.enter">
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<code class="descclassname">scheduler.</code><code class="descname">enter</code><span class="sig-paren">(</span><em>delay</em>, <em>priority</em>, <em>action</em>, <em>argument=()</em>, <em>kwargs={}</em><span class="sig-paren">)</span><a class="headerlink" href="#sched.scheduler.enter" title="Permalink to this definition">¶</a></dt>
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<dd><p>Schedule an event for <em>delay</em> more time units. Other than the relative time, the
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other arguments, the effect and the return value are the same as those for
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<a class="reference internal" href="#sched.scheduler.enterabs" title="sched.scheduler.enterabs"><code class="xref py py-meth docutils literal"><span class="pre">enterabs()</span></code></a>.</p>
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<div class="versionchanged">
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<p><span class="versionmodified">Changed in version 3.3: </span><em>argument</em> parameter is optional.</p>
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<div class="versionadded">
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<p><span class="versionmodified">New in version 3.3: </span><em>kwargs</em> parameter was added.</p>
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<dt id="sched.scheduler.cancel">
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<code class="descclassname">scheduler.</code><code class="descname">cancel</code><span class="sig-paren">(</span><em>event</em><span class="sig-paren">)</span><a class="headerlink" href="#sched.scheduler.cancel" title="Permalink to this definition">¶</a></dt>
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<dd><p>Remove the event from the queue. If <em>event</em> is not an event currently in the
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queue, this method will raise a <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal"><span class="pre">ValueError</span></code></a>.</p>
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<dt id="sched.scheduler.empty">
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<code class="descclassname">scheduler.</code><code class="descname">empty</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#sched.scheduler.empty" title="Permalink to this definition">¶</a></dt>
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<dd><p>Return true if the event queue is empty.</p>
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<dt id="sched.scheduler.run">
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<code class="descclassname">scheduler.</code><code class="descname">run</code><span class="sig-paren">(</span><em>blocking=True</em><span class="sig-paren">)</span><a class="headerlink" href="#sched.scheduler.run" title="Permalink to this definition">¶</a></dt>
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<dd><p>Run all scheduled events. This method will wait (using the <code class="xref py py-func docutils literal"><span class="pre">delayfunc()</span></code>
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function passed to the constructor) for the next event, then execute it and so
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on until there are no more scheduled events.</p>
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<p>If <em>blocking</em> is false executes the scheduled events due to expire soonest
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(if any) and then return the deadline of the next scheduled call in the
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scheduler (if any).</p>
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<p>Either <em>action</em> or <em>delayfunc</em> can raise an exception. In either case, the
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scheduler will maintain a consistent state and propagate the exception. If an
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exception is raised by <em>action</em>, the event will not be attempted in future calls
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to <a class="reference internal" href="#sched.scheduler.run" title="sched.scheduler.run"><code class="xref py py-meth docutils literal"><span class="pre">run()</span></code></a>.</p>
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<p>If a sequence of events takes longer to run than the time available before the
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next event, the scheduler will simply fall behind. No events will be dropped;
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the calling code is responsible for canceling events which are no longer
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<div class="versionadded">
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<p><span class="versionmodified">New in version 3.3: </span><em>blocking</em> parameter was added.</p>
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<dl class="attribute">
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<dt id="sched.scheduler.queue">
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<code class="descclassname">scheduler.</code><code class="descname">queue</code><a class="headerlink" href="#sched.scheduler.queue" title="Permalink to this definition">¶</a></dt>
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<dd><p>Read-only attribute returning a list of upcoming events in the order they
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will be run. Each event is shown as a <a class="reference internal" href="../glossary.html#term-named-tuple"><span class="xref std std-term">named tuple</span></a> with the
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following fields: time, priority, action, argument, kwargs.</p>
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<h3><a href="../contents.html">Table Of Contents</a></h3>
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<li><a class="reference internal" href="#">17.6. <code class="docutils literal"><span class="pre">sched</span></code> — Event scheduler</a><ul>
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<li><a class="reference internal" href="#scheduler-objects">17.6.1. Scheduler Objects</a></li>
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