# 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())

# 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)