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=""