python3 Observer Pattern (Publisher/Subscriber pattern)

example_usage.py

from pubsub import PubSub
from test_classes import Test1, Test2, print_string, add_number

def main():
    bus = PubSub()

    test1 = Test1("hello")
    test2 = Test2(2)

    bus.subscribe(print_string, Test1)
    bus.subscribe(add_number, Test2)

    bus.publish(test1)
    bus.publish(test2)


if __name__ == '__main__':
    main()

pubsub.py

class PubSub:
    def __init__(self):
        self.subscribers = {}

    def subscribe(self, function, message):
        if message not in self.subscribers:
            self.subscribers[message] = []
        self.subscribers[message].append(function)

    def publish(self, message):
        for function in self.subscribers[type(message)]:
            function(message)

test_classes.py

class Test1:
    def __init__(self, string):
        self.message = string


class Test2:
    def __init__(self, int):
        self.int = int


def print_string(message):
    print(message.message)


def add_number(message):
    print(1 + message.int)