使用描述符多实例属性做类型检查

 1 class Attr(object):
 2 
 3     def __init__(self, name, type_):
 4         self.name = name
 5         self.type_ = type_
 6 
 7     def __get__(self, instance, cls):
 8         return instance.__dict__[self.name]
 9 
10     def __set__(self, instance, value):
11         if not isinstance(value, self.type_):
12             raise TypeError('expected an %s'% self.type_)
13 
14         instance.__dict__[self.name] = value
15 
16     def __delete__(self, instance):
17         del instance.__dict__[self.name]
18 
19 
20 
21 class Person(object):
22     name = Attr('name', str)
23     age = Attr('age', int)
24     height = Attr('height', float)
25 
26 
27 
28 p = Person()
29 p.name = 'ray'
30 print(p.name)