代码：
class MyType(type): ???def __init__(self, *args, **kwargs): ???????super(MyType, self).__init__(*args, **kwargs) ???def __call__(self, *args, **kwargs): ???????obj = self.__new__(self, *args, **kwargs) ???????obj.__init__(*args, **kwargs) ???????return objclass Foo(object, metaclass=MyType): ???def __init__(self): ???????print(‘xxx‘)obj = Foo()print(obj)
结果
xxx<__main__.Foo object at 0x0000022688A07EB8>
我们看下面的代码
new
class Foo(object): ???def __init__(self): ???????return ‘init‘ ???def __new__(cls, *args, **kwargs): ???????return ‘new‘obj = Foo()print(obj)
结果 ：new
class Foo(object): ???def __init__(self): ???????return ‘init‘ ???def __new__(cls, *args, **kwargs): ???????return cls.__init__(cls)obj = Foo()print(obj)
结果 init
由此可以看出 实例化对象的过程，__new__()比__init__()先执行
但是 实际上，在这次“”交♂易“”之前还走了一个中间商 那就是type的__call__(),但是我们并看不到__claa__()的源码。
类的metaclass 默认是type。
class MyType(type): ???def __call__(self, *args, **kwargs): ???????return ‘MyType‘class Foo(object, metaclass=MyType): ???def __init__(self): ???????return ‘init‘ ???def __new__(cls, *args, **kwargs): ???????return cls.__init__(cls) ???def __call__(self, *args, **kwargs): ???????return ‘call‘obj = Foo()print(obj)
结果：MyType
扩展参考：https://www.jianshu.com/p/ad976b494486
metaclass
原文地址：https://www.cnblogs.com/0bug/p/8578747.html