python Pool常用函数用法总结

#coding: utf-8
import multiprocessing
import time
 
 
def func(msg):
    print("msg:", msg)
    time.sleep(3)
    print("end")
 
 
if __name__ == "__main__":
    cores = multiprocessing.cpu_count()
    pool = multiprocessing.Pool(processes=cores)
    print("Adding tasks...")
    for i in range(cores):
        msg = "hello %d" %(i)
        pool.apply_async(func, (msg, ))   #维持执行的进程总数为processes，当一个进程执行完毕后会添加新的进程进去
    print("Starting tasks...")
    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("Sub-process(es) done.")

# -*- coding:utf-8 -*-
from multiprocessing import Pool
import os, time, random
def worker(msg):
  t_start = time.time()
  print("%s开始执行,进程号为%d" % (msg,os.getpid()))
  # random.random()随机生成0~1之间的浮点数
  time.sleep(random.random()*2) 
  t_stop = time.time()
  print(msg,"执行完毕，耗时%0.2f" % (t_stop-t_start))
po = Pool(3) # 定义一个进程池，最大进程数3
for i in range(0,10):
  # Pool().apply_async(要调用的目标,(传递给目标的参数元祖,))
  # 每次循环将会用空闲出来的子进程去调用目标
  po.apply_async(worker,(i,))
print("----start----")
po.close() # 关闭进程池，关闭后po不再接收新的请求
po.join() # 等待po中所有子进程执行完成，必须放在close语句之后
print("-----end-----")