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<title>7.8 Queue -- A synchronized queue class</title>
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<H1><A NAME="SECTION009800000000000000000">
7.8 <tt class="module">Queue</tt> --
         A synchronized queue class</A>
</H1>

<P>
<A NAME="module-Queue"></A>

<P>
The <tt class="module">Queue</tt> module implements a multi-producer, multi-consumer
FIFO queue.  It is especially useful in threads programming when
information must be exchanged safely between multiple threads.  The
<tt class="class">Queue</tt> class in this module implements all the required locking
semantics.  It depends on the availability of thread support in
Python.

<P>
The <tt class="module">Queue</tt> module defines the following class and exception:

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><span class="typelabel">class</span>&nbsp;<tt id='l2h-2752' xml:id='l2h-2752' class="class">Queue</tt></b>(</nobr></td>
  <td><var>maxsize</var>)</td></tr></table></dt>
<dd>
Constructor for the class.  <var>maxsize</var> is an integer that sets the
upperbound limit on the number of items that can be placed in the
queue.  Insertion will block once this size has been reached, until
queue items are consumed.  If <var>maxsize</var> is less than or equal to
zero, the queue size is infinite.
</dl>

<P>
<dl><dt><b><span class="typelabel">exception</span>&nbsp;<tt id='l2h-2753' xml:id='l2h-2753' class="exception">Empty</tt></b></dt>
<dd>
Exception raised when non-blocking <tt class="method">get()</tt> (or
<tt class="method">get_nowait()</tt>) is called on a <tt class="class">Queue</tt> object which is
empty.
</dd></dl>

<P>
<dl><dt><b><span class="typelabel">exception</span>&nbsp;<tt id='l2h-2754' xml:id='l2h-2754' class="exception">Full</tt></b></dt>
<dd>
Exception raised when non-blocking <tt class="method">put()</tt> (or
<tt class="method">put_nowait()</tt>) is called on a <tt class="class">Queue</tt> object which is
full.
</dd></dl>

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<span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span>
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