Python 从pubsub回调函数返回值

我试图从pubsub回调函数中获取一个值

如果我在回调函数中打印message.data，我可以看到数据。我曾经尝试过stream\u pull\u future并制作了一个python类，但没有成功

project = 'project_id'
topic = 'topic'
subscription = "sub"
timeout = 10.0

subscriber = pubsub_v1.SubscriberClient()
subscription_path = subscriber.subscription_path(
    project, subscription
)


def test_callback():
    callback_class = CallBackMethod()
    streaming_pull_future = subscriber.subscribe(
        subscription_path, callback=callback_class.callback()
    )

    time.sleep(30)

    print("streaming", streaming_pull_future.result())
    print("streaming_timeout", streaming_pull_future.result(timeout=timeout))

    decoded_string = streaming_pull_future.decode('utf-8')
    print("decoded_string", decoded_string)

    # other stuff with string


class CallBackMethod:
    def __init__(self, data=None):
        self.data = data

    @classmethod
    def callback(cls, message=None):
        info("Got message {}".format(message))
        if message is None:
            return
        return cls(message.data)

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你说“没有成功”是什么意思？你有错误吗？您的意思是永远不会调用回调？请更准确地说明您收到的错误消息，以便其他人可以帮助您！