Python内置函数之-property

property 是一个内置的装饰器函数，只在面向对象中使用

求一个圆的周长和面积

# 周长和面积都是通过类的方法得到
from math import  pi
class Cricle:
    def __init__(self,r):
        self.r = r

    def getPerimeter(self):
        return 2*pi*self.r

    def getArea(self):
        return pi*self.r**2
c1 = Cricle(5)
print(c1.getPerimeter())
print(c1.getArea())

# 人的BMI，它是计算得来得，但更像是一个人的属性

# 传统做法
class  Person:
    def __init__(self,name,high,weight):
        self.name = name
        self.high = high
        self.weight = weight

    def getBIM(self):
        return self.weight/(self.high**2)
    
wangys=Person('wangys',1.75,70)
print(wangys.getBIM())


# perporty
class  Person:
    def __init__(self,name,high,weight):
        self.name = name
        self.high = high
        self.weight = weight

    @property
    def bim(self):
        return self.weight/(self.high**2)

wangys=Person('wangys',1.75,70)
print(wangys.bim)

class Goods: # 定义了一个商品类
    discount = 0.5  # 折扣是5折
    def __init__(self,name,price):
        self.name = name
        self.__price = price # 将需要修改的属性设置成为私有属性
 
    @property
    def price(self): # 定义一个正常的属性，然后做相应的操作
        return  self.__price * Goods.discount

apple = Goods('apple',10)
print(apple.price)

class Persion:
    def __init__(self,name):
        self.__name = name

    @property
    def name(self):
        return self.__name
    @name.setter
    def name(self,new_name):
        self.__name = new_name

# 但是圆的周长和面积更像圆的属性，使用property 将一个函数（无参数）伪装成一个类的属性

from math import  pi
class Cricle:
    def __init__(self,r):
        self.r = r

    @property
    def perimeter(self):
        return 2*pi*self.r
    @property
    def area(self):
        return pi*self.r**2


c1 = Cricle(5)
print(c1.perimeter)
print(c1.area)