[Python]Queue -- A synchronized queue class

Python Queue模块详解

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本文介绍了Python中的Queue模块，该模块实现了一个多生产者、多消费者的第一入先出(FIFO)队列，特别适用于多线程编程中多个线程间安全地交换信息。文章详细解释了Queue类的构造方法及主要方法，如put、get等，并说明了队列满或空时可能抛出的异常。

The Queue 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 Queue class in this module implements all the required locking semantics. It depends on the availability of thread support in Python.

The Queue module defines the following class and exception:

class Queue( maxsize)

Constructor for the class. maxsize 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 maxsize is less than or equal to zero, the queue size is infinite.

exception Empty

Exception raised when non-blocking get() (or get_nowait()) is called on a Queue object which is empty or locked.

exception Full

Exception raised when non-blocking put() (or put_nowait()) is called on a Queue object which is full or locked.

Queue Objects

Class Queue implements queue objects and has the methods described below. This class can be derived from in order to implement other queue organizations (e.g. stack) but the inheritable interface is not described here. See the source code for details. The public methods are:

qsize( )

Return the approximate size of the queue. Because of multithreading semantics, this number is not reliable.

empty( )

Return True if the queue is empty, False otherwise. Becauseof multithreading semantics, this is not reliable.

full( )

Return True if the queue is full, False otherwise. Because of multithreading semantics, this is not reliable.

put( item[, block[, timeout]]

Put item into the queue. If optional args block is true and timeout is None (the default), block if necessary until a free slot is available. If timeout is a positive number, it blocks at most timeout seconds and raises the Full exception if no free slot was available within that time. Otherwise ( block is false), put an item on the queue if a free slot is immediately available, else raise the Full exception ( timeout is ignored in that case).

New in version 2.3: the timeout parameter.

put_nowait( item)

Equivalent to put(item, False).

get( [block[, timeout]])

Remove and return an item from the queue. If optional args block is true and timeout is None (the default), block if necessary until an item is available. If timeout is a positive number, it blocks at most timeout seconds and raises the Empty exception if no item was available within that time. Otherwise ( block is false), return an item if one is immediately available, else raise the Empty exception ( timeout is ignored in that case).

New in version 2.3: the timeout parameter.

get_nowait( )

Equivalent to get(False).