一、创建类的执行流程
二、元类的认识
什么是元类呢？在Python3中继承type的就是元类
二、元类的示例
方式一：
# 方式一class MyType(type): ???‘‘‘继承type的就是元类‘‘‘ ???def __init__(self,*args,**kwargs): ???????print("MyType创建的对象",self) ??#Foo ???????super(MyType,self).__init__(*args,**kwargs) ???def __call__(self, *args, **kwargs): ???????obj = super(MyType,self).__call__(*args,**kwargs) ???????print("类创建对象",self,obj) ??#Fooclass Foo(object,metaclass=MyType): # ?对象加括号会去执行__call__方法，__call__方法里面继承了type的__call__方法 ????????????????????????????????????，type的__call__方法里面会先执行__new__方法，再去执行__init__方法。 ?????????????????????????????????????所以，Foo就是用type创建出来的 ???user = "haiyan" ???age = 18obj = Foo()方式二
# 方式二class MyType(type): ???def __init__(self, *args, **kwargs): ???????print("ssss") ???????super(MyType, self).__init__(*args, **kwargs) ???def __call__(cls, *args, **kwargs): ???????v = dir(cls) ???????obj = super(MyType, cls).__call__(*args, **kwargs) ???????return obj#对象加括号就会去执行__call__方法class Foo(MyType(‘Zcc‘, (object,), {})): ?#MyType(‘Zcc‘, (object,), {})相当于class Zcc(object):pass,也就是创建了一个Zcc的类 ???user = ‘haiyan‘ ???age = 18obj = Foo()方式三
# 方式三class MyType(type): ???def __init__(self, *args, **kwargs): ???????print("ssss") ???????super(MyType, self).__init__(*args, **kwargs) ???def __call__(cls, *args, **kwargs): ???????v = dir(cls) ???????obj = super(MyType, cls).__call__(*args, **kwargs) ???????return obj#对象加括号就会去执行__call__方法def with_metaclass(arg,base): ???print("类对象",MyType(‘Zcc‘, (base,), {})) ???return arg(‘Zcc‘, (base,), {}) ?#返回一个类对象 ?<class ‘__main__.Zcc‘>class Foo(with_metaclass(MyType,object)): ?#MyType(‘Zcc‘, (object,), {})相当于class Zcc(object):pass,也就是创建了一个Zcc的类 ???user = ‘haiyan‘ ???age = 18obj = Foo()=======================附加===========================
1 class ASD(type): 2 ????pass 3 ?4 qqq = ASD("qwe", (object,), {}) ?#用ASD这个元类创建了一个（qwe,并且继承object类的）类 5 ?6 # class ASD(qwe): 7 # ????pass 8 obj = qqq() 9 # 能创建类的是元类10 # 能创建对象的是类11 print(obj) ?#<__main__.qwe object at 0x00000000024FFBA8>12 print(obj.__class__) ?#<class ‘__main__.qwe‘>13 print(obj.__class__.__class__) ?#<class ‘__main__.ASD‘>14 print(obj.__class__.__class__.__class__) ?#<class ‘type‘>15 print(obj.__class__.__class__.__class__.__class__) ?#<class ‘type‘>