使用多处理从不同的进程追加到同一个列表

作者: 首席鉴黄大师
来源: 51数据库
2022-12-08

问题描述

我需要使用 multiprocessing 将来自不同进程的对象附加到一个列表 L ，但它返回空列表.如何让许多进程使用多处理附加到列表 L?

I need to append objects to one list L from different processes using multiprocessing , but it returns empty list. How can I let many processes append to list L using multiprocessing?

#!/usr/bin/python
from multiprocessing import Process

L=[]
def dothing(i,j):
    L.append("anything")
    print i

if __name__ == "__main__":
    processes=[]
    for i in range(5):
        p=Process(target=dothing,args=(i,None))
        p.start()
        processes.append(p)
    for p in processes:
        p.join()

print L

推荐答案

全局变量在进程之间不共享.

Global variables are not shared between processes.

您需要使用 multiprocessing.Manager.list:

You need to use multiprocessing.Manager.list:

from multiprocessing import Process, Manager

def dothing(L, i):  # the managed list `L` passed explicitly.
    L.append("anything")

if __name__ == "__main__":
    with Manager() as manager:
        L = manager.list()  # <-- can be shared between processes.
        processes = []
        for i in range(5):
            p = Process(target=dothing, args=(L,i))  # Passing the list
            p.start()
            processes.append(p)
        for p in processes:
            p.join()
        print L

参见进程间共享状态?(服务器进程部分).

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