#coding: utf-8import multiprocessingimport 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 Poolimport os, time, randomdef 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3for 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-----")