python-patterns/publish_subscribe.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

"""
Reference: http://www.slideshare.net/ishraqabd/publish-subscribe-model-overview-13368808
Author: https://github.com/HanWenfang
"""


class Provider:

    def __init__(self):
        self.msg_queue = []
        self.subscribers = {}

    def notify(self, msg):
        self.msg_queue.append(msg)

    def subscribe(self, msg, subscriber):
        if msg not in self.subscribers:
            self.subscribers[msg] = []
            self.subscribers[msg].append(subscriber)  # unfair
        else:
            self.subscribers[msg].append(subscriber)

    def unsubscribe(self, msg, subscriber):
        self.subscribers[msg].remove(subscriber)

    def update(self):
        for msg in self.msg_queue:
            if msg in self.subscribers:
                for sub in self.subscribers[msg]:
                    sub.run(msg)
        self.msg_queue = []


class Publisher:

    def __init__(self, msg_center):
        self.provider = msg_center

    def publish(self, msg):
        self.provider.notify(msg)


class Subscriber:

    def __init__(self, name, msg_center):
        self.name = name
        self.provider = msg_center

    def subscribe(self, msg):
        self.provider.subscribe(msg, self)

    def run(self, msg):
        print("{} got {}".format(self.name, msg))


def main():
    message_center = Provider()

    fftv = Publisher(message_center)

    jim = Subscriber("jim", message_center)
    jim.subscribe("cartoon")
    jack = Subscriber("jack", message_center)
    jack.subscribe("music")
    gee = Subscriber("gee", message_center)
    gee.subscribe("movie")

    fftv.publish("cartoon")
    fftv.publish("music")
    fftv.publish("ads")
    fftv.publish("movie")
    fftv.publish("cartoon")
    fftv.publish("cartoon")
    fftv.publish("movie")
    fftv.publish("blank")

    message_center.update()


if __name__ == "__main__":
    main()

### OUTPUT ###
# jim got cartoon
# jack got music
# gee got movie
# jim got cartoon
# jim got cartoon
# gee got movie