如何在调用子方法时强制调用父方法？

我想要的是强制当子类从父类继承并且它重写父类方法而不显式调用它时，会引发错误。 在错误类的初始化或调用该方法时可能会引发错误。

目标是确保 Mother 类的用户执行 mother 方法中存在的一些操作。

Example

class Mother():
    def necessary_method(self):
         # do some necessary stuff

class GoodChild(Mother):
    def necessary_method(self):
        # necessary parent call
        super().necessary_method()

class BadChild(Mother):
    def necessary_method(self):
         # no parent call
         return

致电时：

good = GoodChild()
# works fine
bad = BadChild()
# exception could be raised here

good.necessary_method()
# works fine
bad.necessary_method()
# exception could be raised here

这真的可能吗？ 欢迎任何答案或解决方法。

是的，这绝对是可能的，至少在运行时是这样。你可以创建一个Metaclass修改类的创建方式，其想法是改变necessary_method签名通过添加mother_method_called标志只有当Motherversion 被调用，否则会引发Value Error。例如在python3:

class MotherMetaClass(type):
    def __new__(cls, name, bases, attrs):
        method_name = 'necessary_method'
        mother_class_name = 'Mother'
        original_necessary_method = attrs.get(method_name)

        def necessary_method_validated(*args, **kwargs):
            original_necessary_method(*args, **kwargs)

            if name == mother_class_name:
                cls.mother_method_called = True
            else:
                if not cls.mother_method_called:
                    raise ValueError(f'Must call "super()" when overriding "{method_name}".')
                cls.mother_method_called = False

        attrs[method_name] = necessary_method_validated

        return super().__new__(cls, name, bases, attrs)


class Mother(metaclass=MotherMetaClass):
    def necessary_method(self):
        print('Parent method called.')


class GoodChild(Mother):
    def necessary_method(self):
        super().necessary_method()
        print('Good child method called.')


class BadChild(Mother):
    def necessary_method(self):
        print("Bad child method called.")


a = GoodChild()
a.necessary_method()  # it's going to work properly


b = BadChild()
b.necessary_method()  # it's going to raise Value Error