3 进程池

1.  3种方式比较

# fork 父子进程都执行任务  抛弃使用
ret = os.fork()
if ret == 0:
    #子进程
else:
    #父进程


#父进程会等待子进程结束
#主进程，子进程都执行
p1 = Process(target=xxx)
p1.start()


#主进程一般用来等待(join)。。。真正的任务都做子进程中执行 
pool = Pool(30)
pool.apply_async(xxxx)
pool.join()

2.apply堵塞式 不用

from multiprocessing import Pool
import os
import random
import time

def worker(num):
    for i in range(5):
        print("===pid=%d==num=%d="%(os.getpid(), num))
        time.sleep(1)

#3表示 进程池中对多有3个进程一起执行
pool = Pool(3)

for i in range(10):
    print("---%d---"%i)
    pool.apply(worker, (i,))  #堵塞式的方式


pool.close()
pool.join()

---0---
===pid=3197==num=0=
===pid=3197==num=0=
===pid=3197==num=0=
===pid=3197==num=0=
===pid=3197==num=0=
---1---
===pid=3198==num=1=
===pid=3198==num=1=
===pid=3198==num=1=
===pid=3198==num=1=
===pid=3198==num=1=
---2---
===pid=3199==num=2=
===pid=3199==num=2=
===pid=3199==num=2=
===pid=3199==num=2=
===pid=3199==num=2=
---3---
===pid=3197==num=3=
===pid=3197==num=3=
===pid=3197==num=3=
===pid=3197==num=3=