property装饰

property装饰

from math import pi
class Circle:
    def __init__(self,r):
        self.r = r
    @property # 把一个方法伪装成一个属性,在调用这个方法的时候不需要加()就可以直接得到返回值
    def area(self):
        return pi * self.r ** 2
r = Circle(5)
print(r.r)
print(r.area)

import time
class Person:
    def __init__(self,name ,birth):
        self.name = name
        self.birth = birth
    @property  # 装饰的这个方法 不能有参数
    def age(self):
        return time.localtime().tm_year - self.birth

taibai = Person('taibai',2000)
print(taibai.age)

# property的第二个应用场景 : 和私有的属性合作的  -这样可以做到只能查看无法修改
class User:
    def __init__(self,usr,pwd):
        self.usr = usr
        self.__pwd = pwd
    @property
    def pwd(self):
        return self.__pwd
alex = User('alex','sbsbsb')
# print(alex.pwd)
# alex.pwd = 111 #报错
--------------------------------
# class Goods:
#     discount = 0.8
#     def __init__(self,name,origin_price):
#         self.name = name
#         self.__price = origin_price
#     @property
#     def price(self):
#         return self.__price * self.discount
#
# apple = Goods('apple',5)
# print(apple.price)

property进阶
class Goods:
    discount = 0.8
    def __init__(self,name,origin_price):
        self.name = name
        self.__price = origin_price
    @property
    def price(self):
        return self.__price * self.discount

    @price.setter
    def price(self,new_value):
        if isinstance(new_value,int):
            self.__price = new_value

apple = Goods('apple',5)
print(apple.price)   # 调用的是被@property装饰的price
apple.price = 10     # 调用的是被setter装饰的price
print(apple.price)

class Goods:
    discount = 0.8
    def __init__(self,name,origin_price):
        self.name = name
        self.__price = origin_price
    @property
    def price(self):
        return self.__price * self.discount

    @price.setter
    def price(self,new_value):
        if isinstance(new_value,int):
            self.__price = new_value

    @price.deleter
    def price(self):
        del self.__price
apple = Goods('apple',5)
print(apple.price)
apple.price = 'ashkaksk'
del apple.price   # 并不能真的删除什么,只是调用对应的被@price.deleter装饰的方法而已
print(apple.price)

# property进阶
class Goods:
    discount = 0.8
    def __init__(self,name ,origin_price):
        self.name = name
        self.__price = origin_price

    @property
    def price(self):
        return self.__price * self.discount

    @price.setter
    def price(self,new_value):
        if isinstance(new_value,int):
            self.__price = new_value

    @price.deleter
    def price(self):
        del self.__price


apple = Goods('apple',5)
print(apple.price)
apple.price = 9
print(apple.price)
del apple.price   # 并不能真的删除什么,只是调用对应的被@price.deleter装饰的方法而已