为什么这个 multiprocessing.Pool 卡住了？

Question

代码：

from multiprocessing import Pool
print ('parent')
max_processes = 4
def foo(result):
    print (result)
def main():
    pool = Pool(processes=max_processes)
    while True:
        pool.apply_async(foo, 5)
if __name__ == '__main__':
    main()

'parent' 被打印了 5 次，因此创建了初始池。但是没有执行 print(result) 语句。

Answer 1

尝试添加with Pool(processes=max_processes) as pool:

with Pool(processes=max_processes) as pool:
    while True:
        pool.apply_async(foo, 5)
    ...

Warning multiprocessing.pool objects have internal resources that need to be properly managed (like any other resource) by using the pool as a context manager or by calling close() and terminate() manually. Failure to do this can lead to the process hanging on finalization.

Answer 2

您在调用 apply_async 时传递的参数不正确。参数需要在一个元组中（或者其他序列，也许），但你将 5 作为一个裸数字传递。

尝试：

def main():
    pool = Pool(processes=max_processes)
    while True:
        pool.apply_async(foo, (5,)) # make a 1-tuple for the args!

为什么这个 multiprocessing.Pool 卡住了？

Why is this multiprocessing.Pool stuck?

python

pool

multiprocessing

python-3.x