metaclass这个属性叫做元类，它是用来表示这个类是由谁来帮他实例化创建的，说白了，就是相当于自己定制一个类。
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class MyType(type): def __init__(self,*args,**kwargs): print("Mytype __init__",*args,**kwargs) def __call__(self, *args, **kwargs): print("Mytype __call__", *args, **kwargs) obj = self.__new__(self) print("obj ",obj,*args, **kwargs) print(self) self.__init__(obj,*args, **kwargs) return obj def __new__(cls, *args, **kwargs): print("Mytype __new__",*args,**kwargs) return type.__new__(cls, *args, **kwargs) class Foo(object,metaclass=MyType): #python3统一用这种 #__metaclass__ = MyType #python2.7中的写法 def __init__(self,name): self.name = name print("Foo __init__") def __new__(cls, *args, **kwargs): print("Foo __new__",cls, *args, **kwargs) return object.__new__(cls) f = Foo("shuaigaogao")print("f",f)print("fname",f.name) #输出Mytype __new__ Foo (<class 'object'>,) {'__new__': <function Foo.__new__ at 0x0000025EF0EFD6A8>,'__init__': <function Foo.__init__ at 0x0000025EF0EFD620>, '__qualname__': 'Foo', '__module__': '__main__'}Mytype __init__ Foo (<class 'object'>,) {'__new__': <function Foo.__new__ at 0x0000025EF0EFD6A8>, '__init__': <function Foo.__init__ at 0x0000025EF0EFD620>, '__qualname__': 'Foo', '__module__': '__main__'}Mytype __call__ shuaigaogaoFoo __new__ <class '__main__.Foo'>obj <__main__.Foo object at 0x0000025EF0F05048> shuaigaogao<class '__main__.Foo'>Foo __init__f <__main__.Foo object at 0x0000025EF0F05048>fname shuaigaogao |
创建过程如下：
总结：
类的生成 调用 顺序依次是 __new__ --> __init__ --> __call__