Observer.py

from abc import *


class ObservableEngine(Engine):

    def __init__(self):
        self.subscribers = set()

    def subscribe(self, subscriber):
        self.subscribers.add(subscriber)

    def unsubscribe(self, subscriber):
        self.subscribers.remove(subscriber)

    def notify(self, message):
        for sub in self.subscribers:
            sub.update(message)


class AbstractObserver(ABC):

    @abstractmethod
    def update(self):
        pass


class ShortNotificationPrinter(AbstractObserver):

    def __init__(self):
        self.achievements = set()

    def update(self, message):
        self.achievements.add(message["title"])


class FullNotificationPrinter(AbstractObserver):

    def __init__(self):
        self.achievements = list()

    def update(self, message):
        if message not in self.achievements:
            self.achievements.append(message)