from multiprocessing import Pool
import os
import time


def worker(num):
    print("task <%s> is runing <%d>" % (os.getpid(), num))
    time.sleep(2)


def main():
    # 定义一个进程池，最大进程数3
    po = Pool(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, args=(i,))

    print("---start---")
    # 关闭进程池，关闭后po不再接收新的请求
    po.close()
    # 等待po中所有子进程执行完毕，必须放在close语句之后
    po.join()
    print("---end---")


if __name__ == '__main__':
    main()