创建类的两种方式
方式一:class Foo(object,metaclass=type): ???CITY = "bj" ???def func(self,x): ???????return x + 1方式二:Foo = type('Foo',(object,),{'CITY':'bj','func':lambda self,x:x+1})类的演变
演变1:class MyType(type): ???def __init__(self,*args,**kwargs): ???????print('创建类之前') ???????super(MyType,self).__init__(*args,**kwargs) ???????print('创建类之后')Base = MyType('Base',(object,),{})# class Base(object,metaclass=MyType):# ????passclass Foo(Base): ???CITY = "bj" ???def func(self, x): ???????return x + 1演变2:class MyType(type): ???def __init__(self,*args,**kwargs): ???????print('创建类之前') ???????super(MyType,self).__init__(*args,**kwargs) ???????print('创建类之后')def with_metaclass(arg): ???return MyType('Base',(arg,),{}) # class Base(object,metaclass=MyType): passclass Foo(with_metaclass(object)): ???CITY = "bj" ???def func(self, x): ???????return x + 1演变3:class MyType(type): ???def __init__(self,*args,**kwargs): ???????super(MyType,self).__init__(*args,**kwargs)class Foo(object,metaclass=MyType): 总结
1. 默认类由type实例化创建。2. 某个类指定metaclass=MyType，那么当前类的所有派生类都由于MyType创建。3. 实例化对象 ???- type.__init__ ????????????- type.__call__ ???- 类.__new__ ???- 类.__init__metaclass 了解一下
原文地址：https://www.cnblogs.com/iyouyue/p/8981983.html