如何在变量改变时触发另一个对象中的函数。Python

class Subject:
    def __init__(self):
        self._observers = []
        self._state = None

    def attach(self, observer):
        self._observers.append(observer)

    def detach(self, observer):
        self._observers.remove(observer)

    def notify(self):
        for observer in self._observers:
            observer.update(self._state)

    @property
    def state(self):
        return self._state

    @state.setter
    def state(self, value):
        self._state = value
        self.notify()

class Observer:
    def update(self, state):
        print(f"State changed to {state}")

# 示例
subject = Subject()
observer = Observer()
subject.attach(observer)

subject.state = 10  # 输出: State changed to 10

class MyClass:
    def __init__(self):
        self._value = None

    @property
    def value(self):
        return self._value

    @value.setter
    def value(self, new_value):
        self._value = new_value
        self.on_value_change()

    def on_value_change(self):
        print(f"Value changed to {self._value}")

# 示例
obj = MyClass()
obj.value = 20  # 输出: Value changed to 20

def on_change(new_value):
    print(f"Value changed to {new_value}")

class MyClass:
    def __init__(self, callback):
        self._value = None
        self._callback = callback

    @property
    def value(self):
        return self._value

    @value.setter
    def value(self, new_value):
        self._value = new_value
        self._callback(new_value)

# 示例
obj = MyClass(on_change)
obj.value = 30  # 输出: Value changed to 30