python多进程中使用pool

Python 多进程中使用pool，pool中指定每次运行几个进程，当其中一个进程结束完毕后，会加入新的进程

 

 #!/usr/bin/env python
 #coding: utf-8
 import multiprocessing
 import os,time,random

 def Lee():
     print "Run task Lee-%s" %(os.getpid()) #os.getpid()获取当前的进程的ID
     start=time.time()
     time.sleep(random.random()*10) #random.random()随机生成0-1之间的小数
     end=time.time()
     print 'Task Lee, runs %0.2f seconds.' %(end - start)

 def Marlon():
     print "Run task Marlon-%s" %(os.getpid())
     start=time.time()
     time.sleep(random.random()*40)
     end=time.time()
     print 'Task Marlon runs %0.2f seconds.' %(end - start)

 def Allen():
     print "Run task Allen-%s" %(os.getpid())
     start=time.time()
     time.sleep(random.random()*30)
     end=time.time()
     print 'Task Allen runs %0.2f seconds.' %(end - start)

 def Frank():
     print "Run task Frank-%s" %(os.getpid())
     start=time.time()
     time.sleep(random.random()*20)
     end=time.time()
     print 'Task Frank runs %0.2f seconds.' %(end - start)

 if __name__=='__main__':
     function_list=  [Lee,Marlon,Allen,Frank]
     print "parent process %s" %(os.getpid())
     pool=multiprocessing.Pool(2)
     for func in function_list:
         pool.apply_async(func) #Pool执行函数，apply执行函数,当有一个进程执行完毕后，会添加一个新的进程到pool中
     print 'Waiting for all subprocesses done...'
     pool.close()
     pool.join() #调用join之前，一定要先调用close() 函数，否则会出错, close()执行后不会有新的进程加入到pool,join函数等待素有子进程结束
     print 'All subprocesses done.'