Python:使用多重处理从不同进程附加到同一列表 [英] Python:Appending to the same list from different processes using multiprocessing

问题描述

我需要使用多重处理将对象添加到来自不同进程的一个列表"L"中，但是它返回空列表. 我如何使用多重处理让许多进程追加到列表"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

进程之间不共享全局变量.

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

请参见进程之间的共享状态. (服务器进程部分).

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