class Attr(object):    def __init__(self,attrname,attrtype):        self.attrname=attrname        self.attrtype=attrtype    def __get__(self,instance,value):         return instance.__dict__[self.attrname]       def __set__(self,instance,value):        if not isinstance(value,self.attrtype):             raise TypeError("%s type error"%self.attrname)            instance.__dict__[self.attrname]=value    def __delete__(self,instance):            del instance.__dict__[self.attrname]class Person(object):    name=Attr("name",str)    age=Attr("age",int)        p=Person()p.age="23"