<!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"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>queue – Queue class — Eventlet 0.13.0 documentation</title> <link rel="stylesheet" href="../_static/default.css" type="text/css" /> <link rel="stylesheet" href="../_static/pygments.css" type="text/css" /> <script type="text/javascript"> var DOCUMENTATION_OPTIONS = { URL_ROOT: '../', VERSION: '0.13.0', COLLAPSE_INDEX: false, FILE_SUFFIX: '.html', HAS_SOURCE: true }; </script> <script type="text/javascript" src="../_static/jquery.js"></script> <script type="text/javascript" src="../_static/underscore.js"></script> <script type="text/javascript" src="../_static/doctools.js"></script> <link rel="top" title="Eventlet 0.13.0 documentation" href="../index.html" /> <link rel="up" title="Module Reference" href="../modules.html" /> <link rel="next" title="semaphore – Semaphore classes" href="semaphore.html" /> <link rel="prev" title="pools - Generic pools of resources" href="pools.html" /> </head> <body> <div class="related"> <h3>Navigation</h3> <ul> <li class="right" style="margin-right: 10px"> <a href="../genindex.html" title="General Index" accesskey="I">index</a></li> <li class="right" > <a href="../py-modindex.html" title="Python Module Index" >modules</a> |</li> <li class="right" > <a href="semaphore.html" title="semaphore – Semaphore classes" accesskey="N">next</a> |</li> <li class="right" > <a href="pools.html" title="pools - Generic pools of resources" accesskey="P">previous</a> |</li> <li><a href="../index.html">Eventlet 0.13.0 documentation</a> »</li> <li><a href="../modules.html" accesskey="U">Module Reference</a> »</li> </ul> </div> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body"> <div class="section" id="module-eventlet.queue"> <span id="queue-queue-class"></span><h1><tt class="xref py py-mod docutils literal"><span class="pre">queue</span></tt> – Queue class<a class="headerlink" href="#module-eventlet.queue" title="Permalink to this headline">¶</a></h1> <p>Synchronized queues.</p> <p>The <a class="reference internal" href="#module-eventlet.queue" title="eventlet.queue"><tt class="xref py py-mod docutils literal"><span class="pre">eventlet.queue</span></tt></a> module implements multi-producer, multi-consumer queues that work across greenlets, with the API similar to the classes found in the standard <a class="reference external" href="http://docs.python.org/library/queue.html#Queue" title="(in Python v2.7)"><tt class="xref py py-mod docutils literal"><span class="pre">Queue</span></tt></a> and <a class="reference external" href="http://docs.python.org/library/multiprocessing.html#multiprocessing.Queue" title="(in Python v2.7)"><tt class="xref py py-class docutils literal"><span class="pre">multiprocessing</span></tt></a> modules.</p> <p>A major difference is that queues in this module operate as channels when initialized with <em>maxsize</em> of zero. In such case, both <tt class="xref py py-meth docutils literal"><span class="pre">Queue.empty()</span></tt> and <tt class="xref py py-meth docutils literal"><span class="pre">Queue.full()</span></tt> return <tt class="docutils literal"><span class="pre">True</span></tt> and <tt class="xref py py-meth docutils literal"><span class="pre">Queue.put()</span></tt> always blocks until a call to <tt class="xref py py-meth docutils literal"><span class="pre">Queue.get()</span></tt> retrieves the item.</p> <p>An interesting difference, made possible because of greenthreads, is that <tt class="xref py py-meth docutils literal"><span class="pre">Queue.qsize()</span></tt>, <tt class="xref py py-meth docutils literal"><span class="pre">Queue.empty()</span></tt>, and <tt class="xref py py-meth docutils literal"><span class="pre">Queue.full()</span></tt> <em>can</em> be used as indicators of whether the subsequent <tt class="xref py py-meth docutils literal"><span class="pre">Queue.get()</span></tt> or <tt class="xref py py-meth docutils literal"><span class="pre">Queue.put()</span></tt> will not block. The new methods <tt class="xref py py-meth docutils literal"><span class="pre">Queue.getting()</span></tt> and <tt class="xref py py-meth docutils literal"><span class="pre">Queue.putting()</span></tt> report on the number of greenthreads blocking in <tt class="xref py py-meth docutils literal"><span class="pre">put</span></tt> or <tt class="xref py py-meth docutils literal"><span class="pre">get</span></tt> respectively.</p> <dl class="class"> <dt id="eventlet.queue.Queue"> <em class="property">class </em><tt class="descclassname">eventlet.queue.</tt><tt class="descname">Queue</tt><big>(</big><em>maxsize=None</em><big>)</big><a class="headerlink" href="#eventlet.queue.Queue" title="Permalink to this definition">¶</a></dt> <dd><p>Create a queue object with a given maximum size.</p> <p>If <em>maxsize</em> is less than zero or <tt class="docutils literal"><span class="pre">None</span></tt>, the queue size is infinite.</p> <p><tt class="docutils literal"><span class="pre">Queue(0)</span></tt> is a channel, that is, its <tt class="xref py py-meth docutils literal"><span class="pre">put()</span></tt> method always blocks until the item is delivered. (This is unlike the standard <a class="reference internal" href="#eventlet.queue.Queue" title="eventlet.queue.Queue"><tt class="xref py py-class docutils literal"><span class="pre">Queue</span></tt></a>, where 0 means infinite size).</p> <p>In all other respects, this Queue class resembled the standard library, <a class="reference internal" href="#eventlet.queue.Queue" title="eventlet.queue.Queue"><tt class="xref py py-class docutils literal"><span class="pre">Queue</span></tt></a>.</p> <dl class="method"> <dt id="eventlet.queue.Queue.join"> <tt class="descname">join</tt><big>(</big><big>)</big><a class="headerlink" href="#eventlet.queue.Queue.join" title="Permalink to this definition">¶</a></dt> <dd><p>Block until all items in the queue have been gotten and processed.</p> <p>The count of unfinished tasks goes up whenever an item is added to the queue. The count goes down whenever a consumer thread calls <a class="reference internal" href="#eventlet.queue.Queue.task_done" title="eventlet.queue.Queue.task_done"><tt class="xref py py-meth docutils literal"><span class="pre">task_done()</span></tt></a> to indicate that the item was retrieved and all work on it is complete. When the count of unfinished tasks drops to zero, <a class="reference internal" href="#eventlet.queue.Queue.join" title="eventlet.queue.Queue.join"><tt class="xref py py-meth docutils literal"><span class="pre">join()</span></tt></a> unblocks.</p> </dd></dl> <dl class="method"> <dt id="eventlet.queue.Queue.task_done"> <tt class="descname">task_done</tt><big>(</big><big>)</big><a class="headerlink" href="#eventlet.queue.Queue.task_done" title="Permalink to this definition">¶</a></dt> <dd><p>Indicate that a formerly enqueued task is complete. Used by queue consumer threads. For each <tt class="xref py py-meth docutils literal"><span class="pre">get</span></tt> used to fetch a task, a subsequent call to <a class="reference internal" href="#eventlet.queue.Queue.task_done" title="eventlet.queue.Queue.task_done"><tt class="xref py py-meth docutils literal"><span class="pre">task_done()</span></tt></a> tells the queue that the processing on the task is complete.</p> <p>If a <a class="reference internal" href="#eventlet.queue.Queue.join" title="eventlet.queue.Queue.join"><tt class="xref py py-meth docutils literal"><span class="pre">join()</span></tt></a> is currently blocking, it will resume when all items have been processed (meaning that a <a class="reference internal" href="#eventlet.queue.Queue.task_done" title="eventlet.queue.Queue.task_done"><tt class="xref py py-meth docutils literal"><span class="pre">task_done()</span></tt></a> call was received for every item that had been <tt class="xref py py-meth docutils literal"><span class="pre">put</span></tt> into the queue).</p> <p>Raises a <tt class="xref py py-exc docutils literal"><span class="pre">ValueError</span></tt> if called more times than there were items placed in the queue.</p> </dd></dl> </dd></dl> <dl class="class"> <dt id="eventlet.queue.PriorityQueue"> <em class="property">class </em><tt class="descclassname">eventlet.queue.</tt><tt class="descname">PriorityQueue</tt><big>(</big><em>maxsize=None</em><big>)</big><a class="headerlink" href="#eventlet.queue.PriorityQueue" title="Permalink to this definition">¶</a></dt> <dd><p>A subclass of <a class="reference internal" href="#eventlet.queue.Queue" title="eventlet.queue.Queue"><tt class="xref py py-class docutils literal"><span class="pre">Queue</span></tt></a> that retrieves entries in priority order (lowest first).</p> <p>Entries are typically tuples of the form: <tt class="docutils literal"><span class="pre">(priority</span> <span class="pre">number,</span> <span class="pre">data)</span></tt>.</p> </dd></dl> <dl class="class"> <dt id="eventlet.queue.LifoQueue"> <em class="property">class </em><tt class="descclassname">eventlet.queue.</tt><tt class="descname">LifoQueue</tt><big>(</big><em>maxsize=None</em><big>)</big><a class="headerlink" href="#eventlet.queue.LifoQueue" title="Permalink to this definition">¶</a></dt> <dd><p>A subclass of <a class="reference internal" href="#eventlet.queue.Queue" title="eventlet.queue.Queue"><tt class="xref py py-class docutils literal"><span class="pre">Queue</span></tt></a> that retrieves most recently added entries first.</p> </dd></dl> <dl class="class"> <dt id="eventlet.queue.LightQueue"> <em class="property">class </em><tt class="descclassname">eventlet.queue.</tt><tt class="descname">LightQueue</tt><big>(</big><em>maxsize=None</em><big>)</big><a class="headerlink" href="#eventlet.queue.LightQueue" title="Permalink to this definition">¶</a></dt> <dd><p>This is a variant of Queue that behaves mostly like the standard <a class="reference internal" href="#eventlet.queue.Queue" title="eventlet.queue.Queue"><tt class="xref py py-class docutils literal"><span class="pre">Queue</span></tt></a>. It differs by not supporting the <a class="reference internal" href="#eventlet.queue.Queue.task_done" title="eventlet.queue.Queue.task_done"><tt class="xref py py-meth docutils literal"><span class="pre">task_done</span></tt></a> or <a class="reference internal" href="#eventlet.queue.Queue.join" title="eventlet.queue.Queue.join"><tt class="xref py py-meth docutils literal"><span class="pre">join</span></tt></a> methods, and is a little faster for not having that overhead.</p> <dl class="method"> <dt id="eventlet.queue.LightQueue.empty"> <tt class="descname">empty</tt><big>(</big><big>)</big><a class="headerlink" href="#eventlet.queue.LightQueue.empty" title="Permalink to this definition">¶</a></dt> <dd><p>Return <tt class="docutils literal"><span class="pre">True</span></tt> if the queue is empty, <tt class="docutils literal"><span class="pre">False</span></tt> otherwise.</p> </dd></dl> <dl class="method"> <dt id="eventlet.queue.LightQueue.full"> <tt class="descname">full</tt><big>(</big><big>)</big><a class="headerlink" href="#eventlet.queue.LightQueue.full" title="Permalink to this definition">¶</a></dt> <dd><p>Return <tt class="docutils literal"><span class="pre">True</span></tt> if the queue is full, <tt class="docutils literal"><span class="pre">False</span></tt> otherwise.</p> <p><tt class="docutils literal"><span class="pre">Queue(None)</span></tt> is never full.</p> </dd></dl> <dl class="method"> <dt id="eventlet.queue.LightQueue.get"> <tt class="descname">get</tt><big>(</big><em>block=True</em>, <em>timeout=None</em><big>)</big><a class="headerlink" href="#eventlet.queue.LightQueue.get" title="Permalink to this definition">¶</a></dt> <dd><p>Remove and return an item from the queue.</p> <p>If optional args <em>block</em> is true and <em>timeout</em> is <tt class="docutils literal"><span class="pre">None</span></tt> (the default), block if necessary until an item is available. If <em>timeout</em> is a positive number, it blocks at most <em>timeout</em> seconds and raises the <a class="reference internal" href="#eventlet.queue.Empty" title="eventlet.queue.Empty"><tt class="xref py py-class docutils literal"><span class="pre">Empty</span></tt></a> exception if no item was available within that time. Otherwise (<em>block</em> is false), return an item if one is immediately available, else raise the <a class="reference internal" href="#eventlet.queue.Empty" title="eventlet.queue.Empty"><tt class="xref py py-class docutils literal"><span class="pre">Empty</span></tt></a> exception (<em>timeout</em> is ignored in that case).</p> </dd></dl> <dl class="method"> <dt id="eventlet.queue.LightQueue.get_nowait"> <tt class="descname">get_nowait</tt><big>(</big><big>)</big><a class="headerlink" href="#eventlet.queue.LightQueue.get_nowait" title="Permalink to this definition">¶</a></dt> <dd><p>Remove and return an item from the queue without blocking.</p> <p>Only get an item if one is immediately available. Otherwise raise the <a class="reference internal" href="#eventlet.queue.Empty" title="eventlet.queue.Empty"><tt class="xref py py-class docutils literal"><span class="pre">Empty</span></tt></a> exception.</p> </dd></dl> <dl class="method"> <dt id="eventlet.queue.LightQueue.getting"> <tt class="descname">getting</tt><big>(</big><big>)</big><a class="headerlink" href="#eventlet.queue.LightQueue.getting" title="Permalink to this definition">¶</a></dt> <dd><p>Returns the number of greenthreads that are blocked waiting on an empty queue.</p> </dd></dl> <dl class="method"> <dt id="eventlet.queue.LightQueue.put"> <tt class="descname">put</tt><big>(</big><em>item</em>, <em>block=True</em>, <em>timeout=None</em><big>)</big><a class="headerlink" href="#eventlet.queue.LightQueue.put" title="Permalink to this definition">¶</a></dt> <dd><p>Put an item into the queue.</p> <p>If optional arg <em>block</em> is true and <em>timeout</em> is <tt class="docutils literal"><span class="pre">None</span></tt> (the default), block if necessary until a free slot is available. If <em>timeout</em> is a positive number, it blocks at most <em>timeout</em> seconds and raises the <a class="reference internal" href="#eventlet.queue.Full" title="eventlet.queue.Full"><tt class="xref py py-class docutils literal"><span class="pre">Full</span></tt></a> exception if no free slot was available within that time. Otherwise (<em>block</em> is false), put an item on the queue if a free slot is immediately available, else raise the <a class="reference internal" href="#eventlet.queue.Full" title="eventlet.queue.Full"><tt class="xref py py-class docutils literal"><span class="pre">Full</span></tt></a> exception (<em>timeout</em> is ignored in that case).</p> </dd></dl> <dl class="method"> <dt id="eventlet.queue.LightQueue.put_nowait"> <tt class="descname">put_nowait</tt><big>(</big><em>item</em><big>)</big><a class="headerlink" href="#eventlet.queue.LightQueue.put_nowait" title="Permalink to this definition">¶</a></dt> <dd><p>Put an item into the queue without blocking.</p> <p>Only enqueue the item if a free slot is immediately available. Otherwise raise the <a class="reference internal" href="#eventlet.queue.Full" title="eventlet.queue.Full"><tt class="xref py py-class docutils literal"><span class="pre">Full</span></tt></a> exception.</p> </dd></dl> <dl class="method"> <dt id="eventlet.queue.LightQueue.putting"> <tt class="descname">putting</tt><big>(</big><big>)</big><a class="headerlink" href="#eventlet.queue.LightQueue.putting" title="Permalink to this definition">¶</a></dt> <dd><p>Returns the number of greenthreads that are blocked waiting to put items into the queue.</p> </dd></dl> <dl class="method"> <dt id="eventlet.queue.LightQueue.qsize"> <tt class="descname">qsize</tt><big>(</big><big>)</big><a class="headerlink" href="#eventlet.queue.LightQueue.qsize" title="Permalink to this definition">¶</a></dt> <dd><p>Return the size of the queue.</p> </dd></dl> <dl class="method"> <dt id="eventlet.queue.LightQueue.resize"> <tt class="descname">resize</tt><big>(</big><em>size</em><big>)</big><a class="headerlink" href="#eventlet.queue.LightQueue.resize" title="Permalink to this definition">¶</a></dt> <dd><p>Resizes the queue’s maximum size.</p> <p>If the size is increased, and there are putters waiting, they may be woken up.</p> </dd></dl> </dd></dl> <dl class="exception"> <dt id="eventlet.queue.Full"> <em class="property">exception </em><tt class="descclassname">eventlet.queue.</tt><tt class="descname">Full</tt><a class="headerlink" href="#eventlet.queue.Full" title="Permalink to this definition">¶</a></dt> <dd><p>Exception raised by Queue.put(block=0)/put_nowait().</p> </dd></dl> <dl class="exception"> <dt id="eventlet.queue.Empty"> <em class="property">exception </em><tt class="descclassname">eventlet.queue.</tt><tt class="descname">Empty</tt><a class="headerlink" href="#eventlet.queue.Empty" title="Permalink to this definition">¶</a></dt> <dd><p>Exception raised by Queue.get(block=0)/get_nowait().</p> </dd></dl> </div> </div> </div> </div> <div class="sphinxsidebar"> <div class="sphinxsidebarwrapper"> <h4>Previous topic</h4> <p class="topless"><a href="pools.html" title="previous chapter"><tt class="docutils literal"><span class="pre">pools</span></tt> - Generic pools of resources</a></p> <h4>Next topic</h4> <p class="topless"><a href="semaphore.html" title="next chapter"><tt class="docutils literal"><span class="pre">semaphore</span></tt> – Semaphore classes</a></p> <h3>This Page</h3> <ul class="this-page-menu"> <li><a href="../_sources/modules/queue.txt" rel="nofollow">Show Source</a></li> </ul> <div id="searchbox" style="display: none"> <h3>Quick search</h3> <form class="search" action="../search.html" method="get"> <input type="text" name="q" /> <input type="submit" value="Go" /> <input type="hidden" name="check_keywords" value="yes" /> <input type="hidden" name="area" value="default" /> </form> <p class="searchtip" style="font-size: 90%"> Enter search terms or a module, class or function name. </p> </div> <script type="text/javascript">$('#searchbox').show(0);</script> </div> </div> <div class="clearer"></div> </div> <div class="related"> <h3>Navigation</h3> <ul> <li class="right" style="margin-right: 10px"> <a href="../genindex.html" title="General Index" >index</a></li> <li class="right" > <a href="../py-modindex.html" title="Python Module Index" >modules</a> |</li> <li class="right" > <a href="semaphore.html" title="semaphore – Semaphore classes" >next</a> |</li> <li class="right" > <a href="pools.html" title="pools - Generic pools of resources" >previous</a> |</li> <li><a href="../index.html">Eventlet 0.13.0 documentation</a> »</li> <li><a href="../modules.html" >Module Reference</a> »</li> </ul> </div> <div class="footer"> © Copyright 2005-2010, Eventlet Contributors. 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