def __get__(self,instance,owner):
    pass
def __set__(self,instance,value):
    pass
def __delete__(self,instance):
    pass

#DEMOS
class Int_validation:

    def __get__(self, instance, owner):
        return  self.value #owner：<class '__main__.Student'> instance：<__main__.Student object at 0x107e891d0>

    def __set__(self, instance, value):
        if  isinstance(value,int) and 0<value<100:
            self.value=value
        else:
            print("请输入合法的数字")
    def __delete__(self, instance):
        pass

class Student:
    age=9
    #创建一个实例作为另一个类的属性：
    age = Int_validation() #<__main__.Int_validation object at 0x1096999b0>

stu=Student()    #<__main__.Student object at 0x107e891d0>
stu.age=50    #覆盖类属性9
print(stu.age) # 50