小编ret*_*ong的帖子

python3元类的调用顺序

当试图了解metaclass创建类实例的顺序时，我感到困惑。根据此图（源），

我输入以下代码进行验证。

class Meta(type):
    def __call__(self):
        print("Meta __call__")
        super(Meta, self).__call__()

    def __new__(mcs, name, bases, attrs, **kwargs):
        print("Meta __new__")
        return super().__new__(mcs, name, bases, kwargs)

    def __prepare__(msc, name, **kwargs):
        print("Meta __prepare__")
        return {}

class SubMeta(Meta):
    def __call__(self):
        print("SubMeta __call__!")
        super().__call__()

    def __new__(mcs, name, bases, attrs, **kwargs):
        print("SubMeta __new__")
        return super().__new__(mcs, name, bases, kwargs)

    def __prepare__(msc, name, **kwargs):
        print("SubMeta __prepare__")
        return Meta.__prepare__(name, kwargs)

class B(metaclass = SubMeta):
    pass

b = B()

Run Code Online (Sandbox Code Playgroud)

但是，结果似乎不像下面这样。