Python多进程并发(multiprocessing)

A manager returned by Manager() will support types list, dict, Namespace, Lock, RLock, Semaphore, BoundedSemaphore, Condition, Event, Queue, Value and Array. For example,

from multiprocessing import Process, Manager

def f(d, l):
d[1] = '1'
d['2'] = 2
d[0.25] = None
l.reverse()

if __name__ == '__main__':
manager = Manager()

d = manager.dict()
l = manager.list(range(10))

p = Process(target=f, args=(d, l))
p.start()
p.join()

print d
print l
will print

{0.25: None, 1: '1', '2': 2}
[9, 8, 7, 6, 5, 4, 3, 2, 1, 0]

import multiprocessing
import time
def func(msg):
for i in xrange(3):
print msg
time.sleep(1)
if __name__ == "__main__":
pool = multiprocessing.Pool(processes=4)
for i in xrange(10):
msg = "hello %d" %(i)
pool.apply_async(func, (msg, ))
pool.close()
pool.join()
print "Sub-process(es) done."

使用Pool,关注结果

import multiprocessing
import time
def func(msg):
for i in xrange(3):
print msg
time.sleep(1)
return "done " + msg
if __name__ == "__main__":
pool = multiprocessing.Pool(processes=4)
result = []
for i in xrange(10):
msg = "hello %d" %(i)
result.append(pool.apply_async(func, (msg, )))
pool.close()
pool.join()
for res in result:
print res.get()
print "Sub-process(es) done."

#!/usr/bin/env python
#coding=utf-8
"""
Author: Squall
Last modified: 2011-10-18 16:50
Filename: pool.py
Description: a simple sample for pool class
"""

from multiprocessing import Pool
from time import sleep

def f(x):
for i in range(10):
print '%s --- %s ' % (i, x)
#sleep(1)

def main():
pool = Pool(processes=3) # set the processes max number 3
for i in range(11,20):
result = pool.apply_async(f, (i,))
pool.close()
pool.join()
if result.successful():
print 'successful'

if __name__ == "__main__":
main()

先创建容量为3的进程池，然后将f(i)依次传递给它，运行脚本后利用ps aux | grep pool.py查看进程情况，会发现最多只会有三个进程执行。pool.apply_async()用来向进程池提交目标请求，pool.join()是用来等待进程池中的worker进程执行完毕，防止主进程在worker进程结束前结束。但必pool.join()必须使用在pool.close()或者pool.terminate()之后。其中close()跟terminate()的区别在于close()会等待池中的worker进程执行结束再关闭pool,而terminate()则是直接关闭。result.successful()表示整个调用执行的状态，如果还有worker没有执行完，则会抛出AssertionError异常。