python进程池 python进程池

近日学习python的多进程，遇到了一个坑，在此记录一下。
代码如下：

from multiprocessing import Manager, Pool, Lockdef worker(l): for i in range(5): l.append(i) print(l)def callback(arg): print('......exec done ')if __name__ == '__main__': pool = Pool() m = Manager() l = m.list() for _ in range(4): pool.apply_async(worker, args=(l,), callback=callback) pool.close() pool.join() print('Main Process End.')

【python进程池】其中一次输出：

[0, 1, 2, 3, 0, 4, 1] ......exec done: [0, 1, 2, 3, 0, 4, 1, 2, 3, 0, 4] ......exec done: [0, 1, 2, 3, 0, 4, 1, 2, 3, 0, 4, 1, 2, 3, 0, 4, 1] ......exec done: [0, 1, 2, 3, 0, 4, 1, 2, 3, 0, 4, 1, 2, 3, 0, 4, 1, 2, 3, 4] ......exec done: Main Process End.

emmm....好像哪里有些不对....
于是就想到了加锁，修改代码如下:

def worker(l, lock): with lock: for i in range(5): l.append(i) print(l) .... if __name__ == '__main__': pool = Pool() m = Manager() l = m.list() lock = Lock() for _ in range(4): pool.apply_async(worker, args=(l,lock), callback=callback) pool.close() pool.join() print('Main Process End.')

结果发现程序直接就执行了最后一句print('Main Process End.')...
查了一下发现似乎要用Manage，再次修改代码将lock = Lock()替换为lock=m.Lock()

[0, 1, 2, 3, 4] ......exec done: [0, 1, 2, 3, 4, 0, 1, 2, 3, 4] ......exec done: [0, 1, 2, 3, 4, 0, 1, 2, 3, 4, 0, 1, 2, 3, 4] ......exec done: [0, 1, 2, 3, 4, 0, 1, 2, 3, 4, 0, 1, 2, 3, 4, 0, 1, 2, 3, 4] ......exec done: Main Process End.

这次执行结果就和我们想要的一样了。