hereit is in umlobserverinterface core observer observer an observer example the observer pattern might be useful in redundant backup system we can write core object that maintains certain valuesand then have one or more observers create serialized copies of that object these copies might be stored in databaseon remote hostor in local filefor example let' implement the core object using propertiesclass inventorydef __init__(self)self observers [self _product none self _quantity def attach(selfobserver)self observers append(observer@property def product(self)return self _product @product setter def product(selfvalue)self _product value self _update_observers(@property def quantity(self)return self _quantity @quantity setter def quantity(selfvalue)self _quantity value