描述符简单应用示例

#Author : Kelvin
#Date : 2019/1/24 20:57

#实现目标：控制类的实例化对象时传入的参数值

#定义描述符
class Type():
    def __init__(self,key,type):
        self.key=key
        self.type=type
    def __get__(self, instance, owner):
        # print("get")
        return instance.__dict__[self.key]
    def __set__(self, instance, value):
        # print("set")
        if not isinstance(value,self.type):
            raise TypeError("%s Type is not %s"%(self.key,self.type))
        instance.__dict__[self.key]=value
    def __delete__(self, instance):
        # print("delete")
        instance.__dict__.pop(self.key)

#定义类
class People:
    name=Type("name",str)
    age=Type("age",int)
    salary=Type("salary",float)
    def __init__(self,name,age,salary):
        self.name=name
        self.age=age
        self.salary=salary
p1=People("kelvin",18,12800.36)

此时如果实例化对象时，传入的参数不符合条件就会抛出异常！