观察者模式

class Subject:
    def attach(self):
        pass
    def remove(self):
        pass
    def noticefy(self):
        pass
    def getState(self):
        pass
    def setState(self):
        pass

class ConcreteSubject(Subject):
    observer = []
    state = ''
    def attach(self, obj):
        self.observer.append(obj)
    def remove(self, obj):
        self.observer.remove(obj)
    def noticefy(self):
        for i in self.observer:
            i.update()
    def getState(self):
        return self.state
    def setState(self, val):
        self.state = val

class Observer:
    def update(self):
        pass

class EmailObserver(Observer):
    def __init__(self, obj):
        self.subject = obj
    def update(self):
        print('email noticefy user', self.subject.getState())

class LogObserver(Observer):
    def __init__(self, obj):
        self.subject = obj
    def update(self):
        print('log update', self.subject.getState())

if __name__ == '__main__':
    subject = ConcreteSubject()
    subject.attach(EmailObserver(subject))
    subject.attach(LogObserver(subject))
    subject.setState('haha')
    subject.noticefy()