How to Implement a Simple MVVM Binding Mock in Python

class BindingMock:
    def __init__(self, view_model):
        self.view_model = view_model
        self.subscribers = []

    def bind(self, property_name, callback):
        self.subscribers.append((property_name, callback))

    def set(self, property_name, value):
        setattr(self.view_model, property_name, value)
        self.notify(property_name)

    def notify(self, property_name):
        for bound_name, callback in self.subscribers:
            if bound_name == property_name:
                callback(getattr(self.view_model, property_name))


class ViewModel:
    def __init__(self):
        self.user_name = ""
        self.age = 0


class View:
    def __init__(self, view_model):
        self.view_model = view_model
        self.binding = BindingMock(view_model)
        self.binding.bind("user_name", self.update_name_label)
        self.binding.bind("age", self.update_age_label)

    def update_name_label(self, value):
        print(f"Name label updated to: {value}")

    def update_age_label(self, value):
        print(f"Age label updated to: {value}")


if __name__ == "__main__":
    vm = ViewModel()
    view = View(vm)
    view.binding.set("user_name", "Alice")
    view.binding.set("age", 30)