属性查找(元类)

有了元类之后的属性查找

类的属性查找顺序:先从类本身中找--->mro继承关系去父类中找--->去自己定义的元类中找--->type中--->报错

对象的属性查找顺序：先从对象自身找--->类中找--->mro继承关系去父类中找--->报错

举例

class Mymeta(type):
    n=444

    def __call__(self,*args,**kwargs):
        obj=self.__new__(self)
        obj.__init__(*args,**kwargs)
        return obj

class Bar(object):
    # n=333
    pass

class Foo(Bar):
    # n=222
    pass

class OldboyTeacher(Foo,metaclass=Mymeta):
    # n=111
    school='oldboy'

    def __init__(self,name,age):
        self.name=name
        self.age=age

    def say(self):
        print('%s says welcome to the oldboy to learn Python' % self.name)
o=OldboyTeacher('egon',18) #触发OldboyTeacher的类中的__call__方法的执行，进而执行self.__new__开始查找
print(OldboyTeacher.n)