Python多进程共享导入的类

我遇到了一个关于Python多处理共享导入类的问题。问题是这样的：

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

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.

文件B:

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

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.

但是程序运行时会出现错误，即对于每个进程，

Meta

类未初始化，并且每个属性都是

None

。我知道原因是，

Meta

类只在主进程的内存中初始化，每个子进程将独立地拥有自己的原始类Meta

---

但是有什么方法可以让父进程和子进程共享这个类呢？谢谢

您是否考虑过使用multiprocessing.Pool的initializer和initargs参数

为了做到这一点，我稍微修改了您的代码，使其能够运行。它似乎做了你想做的事

档案室

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

档案室

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()

你应该阅读上面的文件。