Python类总结-封装(Property, setter, deleter)

Property

#property
#内置装饰器函数,只在面向对象中使用
from math import pi
class Circle:
    def __init__(self,r ):
        self.r = r
    @property
    def perimeter(self):#property属性不能传递任何参数
        return 2*pi*self.r
    @property
    def area(self):
        return self.r**2*pi
c1 = Circle(5)
# print(c1.area()) #不加property目前定义的是个方法,圆的面积应该是属性,故用@property装饰
print(c1.perimeter) #调用不用加()
print(c1.area)

利用Setter修改Property装饰的变量

class Person:
    def __init__(self, name):
        self.__name = name
    @property
    def name(self):
        return self.__name + 'sb'
    @name.setter #定义一个方法.setter,必须和property装饰同名的方法
    def name(self,new_name):
        self.__name = new_name
        #实现了property装饰的变量的修改操作

tiger = Person('泰哥')
print(tiger.name)
tiger.name = '全部'
print(tiger.name)

>>>>
泰哥sb
全部sb

• Property的实际应用场景 --某个属性需要经过一些计算或操作而得出的结果,通常定义为一个方法然后用Property装饰

class Goods:
    discount = 0.5
    def __init__(self,name, price):
        self.name = name
        self.__price = price #折扣前价格定义为私有的

    @property
    def price(self): #折扣后的价格定义为一个方法并用property装饰,进行一些操作
        return self.__price*Goods.discount

apple = Goods('苹果', 5)
print(apple.price)

Property的删除-deleter

class Person:
    def __init__(self,name):
        self.__name = name
    @property
    def name(self):
        return self.__name
    @name.deleter #property装饰的变量.deleter
    def name(self):
        del self.__name#执行删除私有变量

     @name.setter #设置一个新的变量
    def name(self,new_name): #可以传递一个变量
        self.__name = new name

brother2 = Person('二哥')
print(brother2.name)
del brother2.name #删除某个私有变量
print(brother2.name)

>>>>

二哥
  File "C:/Users/jwang2/PycharmProjects/PlayPy/Demo/S9-day25-封装.py", line 139, in <module>
    print(brother2.name)
  File "C:/Users/jwang2/PycharmProjects/PlayPy/Demo/S9-day25-封装.py", line 131, in name
    return self.__name
AttributeError: 'Person' object has no attribute '_Person__name'