publish-subscribe pattern class publisher(object)def __init__(selfdispatcher)self dispatcher dispatcher def publish(selfmessage)self dispatcher send(messageclass dispatcher(object)def __init__(self)self topic_subscribers dict(def subscribe(selfsubscribertopic)self topic_subscribers setdefault(topicset()add(subscriberdef unsubscribe(selfsubscribertopic)self topic_subscribers setdefault(topicset()discard(subscriberdef unsubscribe_all(selftopic)self subscribers self topic_subscribers[topicset(def send(selfmessage)for subscriber in self topic_subscribers[message topic]subscriber process(messagedef main()dispatcher dispatcher(publisher_ publisher(dispatchersubscriber_ subscriber(dispatcher'topic 'message message(message payload "my payloadmessage topic 'topic publisher_ publish(messageif __name__ ="__main__"main(now we see the code resulting in the message (shown belowprinted by the subscriber messagemy payload