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84 lines
2.9 KiB
TeX
84 lines
2.9 KiB
TeX
\section{\module{Queue} ---
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A synchronized queue class}
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\declaremodule{standard}{Queue}
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\modulesynopsis{A synchronized queue class.}
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The \module{Queue} module implements a multi-producer, multi-consumer
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FIFO queue. It is especially useful in threads programming when
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information must be exchanged safely between multiple threads. The
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\class{Queue} class in this module implements all the required locking
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semantics. It depends on the availability of thread support in
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Python.
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The \module{Queue} module defines the following class and exception:
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\begin{classdesc}{Queue}{maxsize}
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Constructor for the class. \var{maxsize} is an integer that sets the
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upperbound limit on the number of items that can be placed in the
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queue. Insertion will block once this size has been reached, until
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queue items are consumed. If \var{maxsize} is less than or equal to
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zero, the queue size is infinite.
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\end{classdesc}
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\begin{excdesc}{Empty}
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Exception raised when non-blocking \method{get()} (or
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\method{get_nowait()}) is called on a \class{Queue} object which is
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empty or locked.
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\end{excdesc}
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\begin{excdesc}{Full}
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Exception raised when non-blocking \method{put()} (or
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\method{put_nowait()}) is called on a \class{Queue} object which is
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full or locked.
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\end{excdesc}
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\subsection{Queue Objects}
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\label{QueueObjects}
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Class \class{Queue} implements queue objects and has the methods
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described below. This class can be derived from in order to implement
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other queue organizations (e.g. stack) but the inheritable interface
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is not described here. See the source code for details. The public
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methods are:
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\begin{methoddesc}{qsize}{}
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Return the approximate size of the queue. Because of multithreading
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semantics, this number is not reliable.
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\end{methoddesc}
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\begin{methoddesc}{empty}{}
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Return \code{1} if the queue is empty, \code{0} otherwise. Because
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of multithreading semantics, this is not reliable.
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\end{methoddesc}
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\begin{methoddesc}{full}{}
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Return \code{1} if the queue is full, \code{0} otherwise. Because of
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multithreading semantics, this is not reliable.
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\end{methoddesc}
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\begin{methoddesc}{put}{item\optional{, block}}
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Put \var{item} into the queue. If optional argument \var{block} is 1
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(the default), block if necessary until a free slot is available.
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Otherwise (\var{block} is 0), put \var{item} on the queue if a free
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slot is immediately available, else raise the \exception{Full}
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exception.
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\end{methoddesc}
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\begin{methoddesc}{put_nowait}{item}
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Equivalent to \code{put(\var{item}, 0)}.
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\end{methoddesc}
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\begin{methoddesc}{get}{\optional{block}}
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Remove and return an item from the queue. If optional argument
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\var{block} is 1 (the default), block if necessary until an item is
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available. Otherwise (\var{block} is 0), return an item if one is
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immediately available, else raise the
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\exception{Empty} exception.
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\end{methoddesc}
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\begin{methoddesc}{get_nowait}{}
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Equivalent to \code{get(0)}.
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\end{methoddesc}
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