<?xml version="1.0"?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml" lang="en"><head><title>Twisted Documentation: Scheduling tasks for the future</title><link href="../howto/stylesheet.css" type="text/css" rel="stylesheet" /></head><body bgcolor="white"><h1 class="title">Scheduling tasks for the future</h1><div class="toc"><ol></ol></div><div class="content"><span></span><p>Let's say we want to run a task X seconds in the future. The way to do that is defined in the reactor interface <code class="API"><a href="http://twistedmatrix.com/documents/TwistedDocs/TwistedDocs-1.3.0/api/twisted.internet.interfaces.IReactorTime.html" title="twisted.internet.interfaces.IReactorTime">twisted.internet.interfaces.IReactorTime</a></code>:</p><pre class="python"> <span class="py-src-keyword">from</span> <span class="py-src-variable">twisted</span><span class="py-src-op">.</span><span class="py-src-variable">internet</span> <span class="py-src-keyword">import</span> <span class="py-src-variable">reactor</span><span class="py-src-newline"> </span><span class="py-src-nl"> </span><span class="py-src-keyword">def</span> <span class="py-src-identifier">f</span><span class="py-src-op">(</span><span class="py-src-parameter">s</span><span class="py-src-op">)</span><span class="py-src-op">:</span><span class="py-src-newline"> </span><span class="py-src-indent"> </span><span class="py-src-keyword">print</span> <span class="py-src-string">"this will run 3.5 seconds after it was scheduled: %s"</span> <span class="py-src-op">%</span> <span class="py-src-variable">s</span><span class="py-src-newline"> </span><span class="py-src-nl"> </span><span class="py-src-dedent"></span><span class="py-src-variable">reactor</span><span class="py-src-op">.</span><span class="py-src-variable">callLater</span><span class="py-src-op">(</span><span class="py-src-number">3.5</span><span class="py-src-op">,</span> <span class="py-src-variable">f</span><span class="py-src-op">,</span> <span class="py-src-string">"hello, world"</span><span class="py-src-op">)</span><span class="py-src-newline"> </span><span class="py-src-endmarker"></span></pre><p>If we want a task to run every X seconds repeatedly, we can use <code class="API"><a href="http://twistedmatrix.com/documents/TwistedDocs/TwistedDocs-1.3.0/api/twisted.internet.task.LoopingCall.html" title="twisted.internet.task.LoopingCall">twisted.internet.task.LoopingCall</a></code>:</p><pre class="python"> <span class="py-src-keyword">from</span> <span class="py-src-variable">twisted</span><span class="py-src-op">.</span><span class="py-src-variable">internet</span> <span class="py-src-keyword">import</span> <span class="py-src-variable">task</span><span class="py-src-newline"> </span><span class="py-src-nl"> </span><span class="py-src-keyword">def</span> <span class="py-src-identifier">runEverySecond</span><span class="py-src-op">(</span><span class="py-src-op">)</span><span class="py-src-op">:</span><span class="py-src-newline"> </span><span class="py-src-indent"> </span><span class="py-src-keyword">print</span> <span class="py-src-string">"a second has passed"</span><span class="py-src-newline"> </span><span class="py-src-nl"> </span><span class="py-src-dedent"></span><span class="py-src-variable">l</span> <span class="py-src-op">=</span> <span class="py-src-variable">task</span><span class="py-src-op">.</span><span class="py-src-variable">LoopingCall</span><span class="py-src-op">(</span><span class="py-src-variable">runEverySecond</span><span class="py-src-op">)</span><span class="py-src-newline"> </span><span class="py-src-variable">l</span><span class="py-src-op">.</span><span class="py-src-variable">start</span><span class="py-src-op">(</span><span class="py-src-number">1.0</span><span class="py-src-op">)</span> <span class="py-src-comment"># call every second</span><span class="py-src-newline"> </span><span class="py-src-nl"> </span><span class="py-src-comment"># l.stop() will stop the looping calls </span><span class="py-src-endmarker"></span></pre><p>If we want to cancel a task that we've scheduled:</p><pre class="python"> <span class="py-src-keyword">from</span> <span class="py-src-variable">twisted</span><span class="py-src-op">.</span><span class="py-src-variable">internet</span> <span class="py-src-keyword">import</span> <span class="py-src-variable">reactor</span><span class="py-src-newline"> </span><span class="py-src-nl"> </span><span class="py-src-keyword">def</span> <span class="py-src-identifier">f</span><span class="py-src-op">(</span><span class="py-src-op">)</span><span class="py-src-op">:</span><span class="py-src-newline"> </span><span class="py-src-indent"> </span><span class="py-src-keyword">print</span> <span class="py-src-string">"I'll never run."</span><span class="py-src-newline"> </span><span class="py-src-nl"> </span><span class="py-src-dedent"></span><span class="py-src-variable">callID</span> <span class="py-src-op">=</span> <span class="py-src-variable">reactor</span><span class="py-src-op">.</span><span class="py-src-variable">callLater</span><span class="py-src-op">(</span><span class="py-src-number">5</span><span class="py-src-op">,</span> <span class="py-src-variable">f</span><span class="py-src-op">)</span><span class="py-src-newline"> </span><span class="py-src-variable">callID</span><span class="py-src-op">.</span><span class="py-src-variable">cancel</span><span class="py-src-op">(</span><span class="py-src-op">)</span><span class="py-src-newline"> </span><span class="py-src-endmarker"></span></pre></div><p><a href="../howto/index.html">Index</a></p><span class="version">Version: 1.3.0</span></body></html>