Implementing Observer pattern in Python

The Observer pattern is a behavioral design pattern used to establish one to many dependencies between objects. When an object changes state, all objects that depend on it will be notified and automatically updated. In Python, you can use the built-in Observer pattern implementation. The following is a simple example code to demonstrate how to use Python to implement the Observer pattern: python class Subject: def __init__(self): self._observers = [] def attach(self, observer): self._observers.append(observer) def detach(self, observer): self._observers.remove(observer) def notify(self, message): for observer in self._observers: observer.update(message) class Observer: def __init__(self, name): self._name = name def update(self, message): print(f"{self._name} received message: {message}") #Create Theme Object subject = Subject() #Creating Observer Objects observer1 = Observer("Observer1") observer2 = Observer("Observer2") observer3 = Observer("Observer3") #Add Observer to Theme Object subject.attach(observer1) subject.attach(observer2) subject.attach(observer3) #Send notifications to all observers subject.notify("Hello, Observers!") #Remove an Observer subject.detach(observer2) #Send another notification to the remaining observers subject.notify("Goodbye, Observer2!") In the example code above, the 'Subject' class is the subject object responsible for managing observers. It includes methods such as' attach ',' detach ', and' notify '` The 'attach' method is used to add observers to the topic object, the 'detach' method is used to remove observers, and the 'notify' method is used to send notifications to all observers. `The Observer class is an observer object that contains the 'update' method to handle received notifications. In the sample code, the Observer pattern is implemented by creating the subject and observer objects and calling the corresponding methods. When the 'notify' method is called, the subject object will sequentially call the 'update' method of each observer and pass the corresponding message. Note: Python also has a simpler implementation of the Observer pattern, using the built-in 'Observable' and 'Observer' classes. However, this method has been abandoned in Python 3, so it is not recommended to use it. It is recommended to implement the Observer pattern in the above example code.