Observer

main.py

if __name__ == "__main__":
    stock_watcher = Observable()
 
    american_observer = AmericanStockMarket()
    stock_watcher.register(american_observer)
 
    stock_watcher.publish('KLSE Market Update', price='+0.5')

observable.py

class Observable(object):
 
    def __init__(self):
        self.observers = []
 
    def register(self, observer):
        if not observer in self.observers:
            self.observers.append(observer)
 
    def unregister(self, observer):
        if observer in self.observers:
            self.observers.remove(observer)
 
    def unregister_all(self):
        if self.observers:
            del self.observers[:]
 
    def publish(self, *args, **kwargs):
        for observer in self.observers:
            observer.update(*args, **kwargs)

observer.py

class Observer(object):
    __metaclass__ = ABCMeta
 
    @abstractmethod
    def update(self, *args, **kwargs):
        pass