Python3之无法在进程池中使用队列Queue的解决方案

import multiprocessingimport timeclass Test:    def __init__(self):        self.pool = multiprocessing.Pool()        # self.queue = multiprocessing.Queue()        m = multiprocessing.Manager()        self.queue = m.Queue()    def subprocess(self):        for i in range(10):            print("Running")            time.sleep(1)        print("Subprocess Completed")    def start(self):        self.pool.apply_async(func=self.subprocess)        print("Subprocess has been started")        self.pool.close()        self.pool.join()    def __getstate__(self):        self_dict = self.__dict__.copy()        del self_dict['pool']        return self_dict    def __setstate__(self, state):        self.__dict__.update(state)if __name__ == '__main__':    test = Test()    test.start()

主要是这两行代码：

m = multiprocessing.Manager()self.queue = m.Queue()

A manager object returned by Manager() controls a server process which holds Python objects and allows other processes to manipulate them using proxies.

A manager returned by Manager() will support types list, dict, Namespace, Lock, RLock, Semaphore, BoundedSemaphore, Condition, Event, Barrier, Queue, Value and Array.

共享数据主要通过在内存中共享某个数据类型实现的，共享数据类型比较多：列表，字典，同步锁，递归锁，信号量，时间，还有队列等，这个进程池用的就是共享数据的队列类型数据

话说__getstate__和__setstate__是什么鬼？

这个是Python中有些无法被pickle序列化的对象，调用这两个方法后就可以进行pickle序列化和反序列化处理处理。示例：

class Foo(object):    def __init__(self, val=2):        self.val = val    def __getstate__(self):        # print("I'm being pickled")        self.val *= 2        print(self.__dict__)        return self.__dict__        print('=--------->')    def __setstate__(self, d):        # print("I'm being unpickled with these values:", d)        self.__dict__ = d        # self.val *= 3        # pass        print('============>')import picklef = Foo()f_string = pickle.dumps(f)f_new = pickle.loads(f_string)print(f_new.val)

上面的示例可以很好的解释了__getstate__和__setstate__用法，Python 将只 pickle 当它调用该实例的__getstate__() 方法时返回给它的值，在 unpickle 时，Python 将提供经过 pickle 的值作为参数传递给实例的__setstate__() 方法。在 __setstate__() 方法内，可以根据经过 pickle 的名称和位置信息来重建对象，并将该对象分配给这个实例的 属性。
这个博客写的超级赞：
pickle序列化全接触