sample.py

# mylibrary/library.py


class Library:
    def subscribe(self, topic):
        # checks to see if already subscribed
        if topic in self.topics:
            raise AssertionError("Topic is already subscribed too")

        def wrapper(handler):
            # checks to see if this is part of a class
            if not self._is_method(handler):
                self.client.subscribe(topic)
                print(f"--> subscribed to {topic}")
                self.topics[topic] = handler
            # appends a couple of poperties to the function or method
            handler.subscription = True
            handler.topic = topic
            return handler

        return wrapper

    @staticmethod
    def subscribe2(topic):
        # Removes check so logic must be handled in regsiter
        def wrapper(handler):
            handler.subscription = True
            handler.topic = topic
            return handler

        return wrapper


# status/controller.py


class StatusController:
    """

    How can i access the app instance here? I have a series of methods which register the topic and the apprioate handler. It works fine if i leave the controller in main.py.

    I feel like i'm most likely barking up the wrong tree. It works fine if i convert it to a Static method, but then my app.register method needs to handle the verification, etc.

    I have tried inheritence, adding a library object to the class but to no avail.

    """
    @library.subscribe("some.topic")
    def some_handler(self, payload):
        print(payload)

    @Library.subscribe("some.topic")
    def some_handler1(self, payload):
        print(payload)


# main.py
"""
from mylibrary import Library
from mypackage import StatusController
"""

app = Library()

app.register(StatusController())

app.start()