python 并行处理数据

import multiprocessing
import time
import os
print("温馨提示：本机为",os.cpu_count(),"核CPU")  
 
def func(msg):
    print "msg:", msg
    time.sleep(3)
    print "end"
 
if __name__ == "__main__":
    #这里开启了4个进程
    pool = multiprocessing.Pool(processes = 4)
    for i in xrange(4):
        msg = "hello %d" %(i)
        pool.apply_async(func, (msg, ))   
 
    pool.close()
    pool.join()   #调用join之前，先调用close函数，否则会出错。执行完close后不会有新的进程加入到pool,join函数等待所有子进程结束
    print "Successfully"