进程池

初识进程池

场景一：主进程不会等进程池内部的任务执行完毕后再执行，而是直接执行，进程池内部的任务，自己处理

import os,time
from concurrent.futures import ProcessPoolExecutor,ThreadPoolExecutor


def task(num):
    print("子进程的pid:",os.getpid())
    print("执行：",num)
    time.sleep(2)


if __name__ == '__main__':
    #创建一个进程池，进程池里四个进程
    pool = ProcessPoolExecutor(4)
    for i in range(10):
        pool.submit(task,i)
    #打印abc,不会等待进程池里的内容执行完，而是直接执行
    print("a")
    print("b")
    print("c")

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场景二：200个任务交给进程池去处理，进程池内部的任务处理完成后，再执行某些功能，需要人为做一些阻塞的操作。

import os,time
from concurrent.futures import ProcessPoolExecutor,ThreadPoolExecutor


def task(num):
    print("子进程的pid:",os.getpid())
    print("执行：",num)
    time.sleep(2)


if __name__ == '__main__':
    #创建一个进程池，进程池里四个进程
    pool = ProcessPoolExecutor(4)
    for i in range(10):
        pool.submit(task,i)

    #等待进程池中的任务都执行完毕后，再继续完后执行
    pool.shutdown(True)
    print("a")
    print("b")
    print("c")

image.png

场景三：进程池里拿了一个进程，进行操作，操作结束后，还想做另外的操作，加回调函数的功能。

import os,time
import multiprocessing
from concurrent.futures import ProcessPoolExecutor,ThreadPoolExecutor


def task(num):、
    print("子任务:",multiiprocessing.current_process().pid)
    print("执行：",num)
    time.sleep(2)
    return num

def done(res):
    print("done函数里的的current_process:",multiprocessing.current_process())
    time.sleep(1)
    print("done函数里获取的返回结果：",res.result())
    time.sleep(1)


if __name__ == '__main__':
    #创建一个进程池，进程池里四个进程
    pool = ProcessPoolExecutor(4)
    for i in range(10):
        fur = pool.submit(task,i)
        fur.add_done_callback(done) #done的调用由主进程处理（与线程池不同）

    print("主进程的current_process:", multiprocessing.current_process())
    #等待进程池中的任务都执行完毕后，再继续完后执行
    pool.shutdown(True)
    print("a")
    print("b")
    print("c")

image.png
image.png

进程池+进程锁

import os,time
import multiprocessing
from concurrent.futures import ProcessPoolExecutor,ThreadPoolExecutor


def task(lock):
    print("开始")

    #假设文件中保存的内容就是一个值：10
    with open ("f1.txt",mode = "r",encoding = "utf-8") as f:
        current_num = int(f.read())

    print("排队抢票了")
    time.sleep(0.5)
    current_num -= 1
    with open("f1.txt",mode = "w",encoding = "utf-8") as f:
        f.write(str(current_num))


if __name__ == '__main__':
    pool = ProcessPoolExecutor()
    manager = multiprocessing.Manager()
    lock_object = manager.RLock()
    for i in range(10):
        pool.submit(task,lock_object)