分别实现__get__,__set__,__delete__方法，在__set__内使用isinstance函数做类型检查
# 如何使用描述符对实例属性做类型检查,分别实现set,方法,
# 在set内使用isinstance做类型检查
class Attr(object):
def __init__(self, name, type_):
self.name = name
self.type_ = type_
def __get__(self, instance, cls):
print('in__get__', instance, cls)
return instance.__dict__[self.name]
def __set__(self, instance, value):
print('in__set__')
if not isinstance(value, self.type_):
raise TypeError("expacted is %s" % (self.type_))
instance.__dict__[self.name] = value
def __delete__(self, instance):
print('in__delete__')
del instance.__dict__[self.name]
class Person(object):
name = Attr('name', str)
age = Attr('age', int)
height = Attr('height', float)
p = Person()
p.name = 'oobj'
p.age = 26
print(p.name)
print(p.age)
