面向对象组合小练习

这个代码时计算圆环的周长和面积的

from math import pi
class Circle:
     def __init__(self,r):
         self.r = r
     def area(self):
         return self.r**2 * pi
     def long(self):
         return pi*2*self.r
class Ring:
    def __init__(self,outside_r,inside_r):
        print(self.__dict__)
        self.outside_r=Circle(outside_r)
        self.inside_r=Circle(inside_r)
        print(self.__dict__)

    def ring_area(self):
        return Circle.area(self.outside_r)-Circle.area(self.inside_r)
    def ring_long(self):
        return Circle.long(self.outside_r)-Circle.long(self.inside_r)
ring1=Ring(500,1)
print(ring1.ring_area())
print(ring1.ring_long())
print(ring1.__dict__)