[Python]核心编程之生产者-消费者和Queue模块

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本文介绍如何使用Python的Queue模块实现生产者-消费者模式。通过创建队列对象，生产者线程将数据放入队列，而消费者线程从队列中获取数据。文章提供了具体的代码示例，并解释了队列模块的主要方法。

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Queue模块可以用来进行线程间通信，让各个线程之间共享数据。现在，我们创建一个队列，让生产者（线程）把新生产的货物放进去供消费者（线程）使用，为了达到这个目的，我们要用到Queue模块的以下属性：

通用队列模块属性

Function/Method	Description
`Queue` Module Function
`queue(size)`	Creates a `Queue` object of given`size`
`Queue` Object Methods
`qsize()`	Returns queue size (approximate, since queue may be getting updated by other threads)
`empty()`	Returns `TRue` if queue empty,`False` otherwise
`full()`	Returns `true` if queue full,`False` otherwise
`put(item, block=0)`	Puts `item` in queue, if `block` given (not 0), block until room is available
`get(block=0)`	Gets `item` from queue, if `block` given (not 0), block until an item is available

生产者-消费者问题(procons.py)：

#! /usr/bin/env python
#coding=utf-8
from random import randint
from time import sleep
from Queue import Queue
from myThread import MyThread

def writeQ(queue):
    print("producing object for Q...")
    queue.put("xxx",1)
    print("size now: %d"%queue.qsize())
    
def readQ(queue):
    val = queue.get(1)
    print("consumed object from Q... size now : %d"%queue.qsize())
    
def writer(queue,loops):
    for i in range(loops):
        writeQ(queue)
        sleep(randint(1,3))
        
def reader(queue,loops):
    for i in range(loops):
        readQ(queue)
        sleep(randint(2,5))
        
funcs = [writer,reader]
nfuncs = range(len(funcs))

def main():
    nloops = randint(2,10)
    q = Queue(32)
    threads = []
    for i in nfuncs:
        t = MyThread(funcs[i],(q,nloops),funcs[i].__name__)
        threads.append(t)
        
    for i in nfuncs:
        threads[i].start()
        
    for i in nfuncs:
        threads[i].join()
    
    print("...main completed")
    
if __name__ == "__main__":
    main()

>>>

starting writer at: Sat Jul 26 00:33:08 2014
producing object for Q...
size now: 1
starting reader at: Sat Jul 26 00:33:08 2014
consumed object from Q... size now : 0
producing object for Q...
size now: 1
consumed object from Q... size now : 0
producing object for Q...
size now: 1
producing object for Q...
size now: 2
producing object for Q...
size now: 3
consumed object from Q... size now : 2
producing object for Q...
size now: 3
writer done at: Sat Jul 26 00:33:19 2014
consumed object from Q... size now : 2
consumed object from Q... size now : 1
consumed object from Q... size now : 0
reader done at: Sat Jul 26 00:33:33 2014
...main completed

[myThread.py]

#! /usr/bin/env python
#coding=utf-8
import threading
from time  import ctime

class MyThread(threading.Thread):
    def __init__(self,func,args,name=''):
        threading.Thread.__init__(self)
        self.func = func
        self.args = args
        self.name = name
        
    def getResult(self):
        return self.res
    
    def run(self):
        print("starting %s at: %s"%(self.name,ctime()))
        self.res = apply(self.func,self.args)
        print("%s done at: %s"%(self.name,ctime()))

REF:Core Python Programming