Question

我在Python多处理共享导入的Class上遇到了问题。陷入困境的部分是这样的：

文件A：

class Meta:
    db_a = None
    db_b = None
    ...
# class will be initialized at the very beginning of the program and might
# be imported by all other models globally for a global variable/instance
# access, for example, a global DB access instance is in Meta

文件B：

from file_A import Meta
def runner():
    initialize_meta_db()  # Meta's attributes now have values
    ...
    pool = multiprocessing.Pool(4)
    pool.map(worker, arg_list)
    pool.close()
    pool.join()
    ...

def worker(*args):
    ...
    print(Meta.db_a)  # process will print None
    ...
# a runner function which spawns 4 processes, each process will use class Meta
# to do some work.

但程序运行的错误是每个进程都没有初始化Meta类，每个属性都是None。我知道为什么Meta类只在主进程的内存中初始化，并且每个子进程将独立拥有自己的原始类Meta。

但有什么方法可以与父进程和子进程共享此类？谢谢！

Answer 1

您是否考虑过使用multiprocessing.Pool的初始值设定项和initargs参数？

我稍微修改了你的代码以便能够运行。它似乎做你想要的。

FILE_A

class Meta:
    db_a = None
    db_b = None
    @classmethod
    def initialize_meta_db(cls, db_a='a', db_b='b'):
        Meta.db_a = db_a
        Meta.db_b = db_b

FILE_B

import multiprocessing

from file_A import Meta

def runner():
    Meta.initialize_meta_db()  # Meta's attributes now have values
    pool = multiprocessing.Pool(4, init, '')
    pool.map(worker, (1, 2, 3, 4))
    pool.close()
    pool.join()

def init(*initargs):
    from file_A import Meta
    Meta.initialize_meta_db()

def worker(*args):
    print('Worker {} -- Work {}'.format(args, Meta.db_a))

if __name__ == '__main__':
    runner()

Python多进程共享导入的类

1 个答案: