python元编程3【type类继承和__new__，__init__参数传递】

class SetterAwareType(type):    # 元类
    def __new__(cls, *args):
        # print('in SetterAwareType __new__')
        # print(type(type.__new__(cls, 'hehehe',(object,), {})))
        return type.__new__(cls, 'hehehe',(object,), {})  # 'name' 直接传入了

    def __init__(cls,  *args):
        '''
        # 这里的init不是self，传入的是__new__类似的，打印print(cls, args)结果如下
        1. a = ModelObject()
        2. class C(a)
        1. <class '__main__.hehehe'> ()
        2. <class '__main__.hehehe'> ('C', (<class '__main__.hehehe'>,), {'__module__': '__main__', '__qualname__': 'C', '__init__': <function C.__init__ at 0x000001B83DDC68B8>})
        '''
        # print(cls, args)
        # print('in SetterAwareType __init__')
        # return super(SetterAwareType, cls).__init__(cls,  *args)   # 创建 class C(a) 时候报错 type.__init__() takes 1 or 3 arguments
        return super(SetterAwareType, cls).__init__(cls, )
        # return type.__init__(cls, *args)                    # TypeError: type.__init__() takes 1 or 3 arguments


class ModelObject(SetterAwareType):
    def test(self):
        print('in ModelObject copy')

a = ModelObject()  # _init__ 参数 <class '__main__.hehehe'> ()

class C(a): # _init__ 参数 <class '__main__.hehehe'> ('C', (<class '__main__.hehehe'>,), {'__module__': '__main__', '__qualname__': 'C', '__init__': <function C.__init__ at 0x000002445ED868B8>})
    pass

print(type(SetterAwareType))  #  type 元类
print(type(ModelObject))      #  type 元类

print('a', a)
print(type(a))    # a 是class hehehe，属于ModelObject class

b=a()
print('b', b)
print(type(b))    # b 是obj hehehe，属于hehehe class


a.test()          # 类中的函数
# b.test()        #obj中报错 # AttributeError: 'hehehe' object has no attribute 'test'

c = C()
# c.test()          # AttributeError: 'hehehe' object has no attribute 'test'