使用描述符多实例属性做类型检查

class Attr(object):

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

    def __get__(self, instance, cls):
        return instance.__dict__[self.name]

    def __set__(self, instance, value):
        if not isinstance(value, self.type_):
            raise TypeError('expected an %s'% self.type_)

        instance.__dict__[self.name] = value

    def __delete__(self, instance):
        del instance.__dict__[self.name]



class Person(object):
    name = Attr('name', str)
    age = Attr('age', int)
    height = Attr('height', float)



p = Person()
p.name = 'ray'
print(p.name)