Python多進程機制實例詳解

更新時間：2015年07月02日 11:15:54 作者：tianmo2010

這篇文章主要介紹了Python多進程機制,以實例形式詳細分析了Python多進程機制的原理與實現(xiàn)技巧,需要的朋友可以參考下

本文實例講述了Python多進程機制。分享給大家供大家參考。具體如下：

在以前只是接觸過PYTHON的多線程機制，今天搜了一下多進程，相關(guān)文章好像不是特別多。看了幾篇，小試了一把。程序如下，主要內(nèi)容就是通過PRODUCER讀一個本地文件，一行一行的放到隊列中去。然后會有相應的WORKER從隊列中取出這些行。

import multiprocessing
import os
import sys
import Queue
import time
def writeQ(q,obj):
    q.put(obj,True,None)
    print "put size: ",q.qsize()
def readQ(q):
    ret = q.get(True,1)
    print "get size: ",q.qsize()
    return ret
def producer(q):
    time.sleep(5)  #讓進行休息幾秒 方便ps命令看到相關(guān)內(nèi)容
    pid = os.getpid()
    handle_file = '/home/dwapp/joe.wangh/test/multiprocess/datafile'
    with open(handle_file,'r') as f:   #with...as... 這個用法今天也是第一次看到的
        for line in f:
            print "producer <" ,pid , "> is doing: ",line
            writeQ(q,line.strip())
    q.close()
def worker(q):
    time.sleep(5)  #讓進行休息幾秒 方便ps命令看到相關(guān)內(nèi)容
    pid = os.getpid()
    empty_count = 0
    while True:
        try:
            task = readQ(q)
            print "worker <" , pid , "> is doing: " ,task
            '''
            如果這里不休眠的話 一般情況下所有行都會被同一個子進程讀取到 為了使實驗效果更加清楚 在這里讓每個進程讀取完
一行內(nèi)容時候休眠5s 這樣就可以讓其他的進程到隊列中進行讀取
            '''
            time.sleep(5)  
        except Queue.Empty:
            empty_count += 1
            if empty_count == 3:
                print "queue is empty, quit"
                q.close()
                sys.exit(0)
def main():
    concurrence = 3
    q = multiprocessing.Queue(10)
    funcs = [producer , worker]
    for i in range(concurrence-1):
        funcs.append(worker)
    for item in funcs:
        print str(item)
    nfuncs = range( len(funcs) )
    processes = []    
    for i in nfuncs:
        p = multiprocessing.Process(target=funcs[i] , args=(q,))
        processes.append(p)
    print "concurrence worker is : ",concurrence," working start"
    for i in nfuncs:
        processes[i].start()
    for i in nfuncs:
        processes[i].join()
    print "all DONE"
if __name__ == '__main__':
    main()

實驗結(jié)果如下：

dwapp@pttest1:/home/dwapp/joe.wangh/test/multiprocess>python 1.py 
<function producer at 0xb7b9141c>
<function worker at 0xb7b91454>
<function worker at 0xb7b91454>
<function worker at 0xb7b91454>
concurrence worker is : 3 working start
producer < 28320 > is doing: line 1
put size: 1
producer < 28320 > is doing: line 2
put size: 2
producer < 28320 > is doing: line 3
put size: 3
producer < 28320 > is doing: line 4
put size: 3
producer < 28320 > is doing: line 5
get size: 3
put size: 4
worker < 28321 > is doing: line 1
get size: 3
worker < 28322 > is doing: line 2
get size: 2
worker < 28323 > is doing: line 3
get size: 1
worker < 28321 > is doing: line 4
get size: 0
worker < 28322 > is doing: line 5
queue is empty, quit
queue is empty, quit
queue is empty, quit
all DONE

程序運行期間在另外一個窗口進行ps命令可以觀測到一些進程的信息

dwapp@pttest1:/home/dwapp/joe.wangh/test/multiprocess>ps -ef | grep python
dwapp  13735 11830 0 Nov20 pts/12  00:00:05 python
dwapp  28319 27481 8 14:04 pts/0  00:00:00 python 1.py
dwapp  28320 28319 0 14:04 pts/0  00:00:00 python 1.py
dwapp  28321 28319 0 14:04 pts/0  00:00:00 python 1.py
dwapp  28322 28319 0 14:04 pts/0  00:00:00 python 1.py
dwapp  28323 28319 0 14:04 pts/0  00:00:00 python 1.py
dwapp  28325 27849 0 14:04 pts/13  00:00:00 grep python
dwapp@pttest1:/home/dwapp/joe.wangh/test/multiprocess>ps -ef | grep python
dwapp  13735 11830 0 Nov20 pts/12  00:00:05 python     #此時28320進程 也就是PRODUCER進程已經(jīng)結(jié)束
dwapp  28319 27481 1 14:04 pts/0  00:00:00 python 1.py
dwapp  28321 28319 0 14:04 pts/0  00:00:00 python 1.py
dwapp  28322 28319 0 14:04 pts/0  00:00:00 python 1.py
dwapp  28323 28319 0 14:04 pts/0  00:00:00 python 1.py
dwapp  28328 27849 0 14:04 pts/13  00:00:00 grep python
dwapp@pttest1:/home/dwapp/joe.wangh/test/multiprocess>ps -ef | grep python
dwapp  13735 11830 0 Nov20 pts/12  00:00:05 python
dwapp  28319 27481 0 14:04 pts/0  00:00:00 python 1.py
dwapp  28321 28319 0 14:04 pts/0  00:00:00 python 1.py
dwapp  28322 28319 0 14:04 pts/0  00:00:00 python 1.py
dwapp  28323 28319 0 14:04 pts/0  00:00:00 [python] <defunct>  #這里應該是代表28323進程（WORKER）已經(jīng)運行結(jié)束了
dwapp  28331 27849 0 14:04 pts/13  00:00:00 grep python
dwapp@pttest1:/home/dwapp/joe.wangh/test/multiprocess>ps -ef | grep python
dwapp  13735 11830 0 Nov20 pts/12  00:00:05 python
dwapp  28337 27849 0 14:05 pts/13  00:00:00 grep python

希望本文所述對大家的Python程序設(shè)計有所幫助。

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