python学习day23 组合
组合:一个对象的属性值是另外一个类的对象
比如:alex.weapon 是 Weapon类的对象 ---> alex.weapon.hand18
练习
from math import pi class Circle: def __init__(self,r): self.r = r def area(self): return self.r**2 * pi def perimeter(self): return 2*pi*self.r class Ring: def __init__(self,outside_r,inside_r): self.outside_c = Circle(outside_r) # 属性值是另外一个类的对象 self.inside_c = Circle(inside_r) def area(self): return self.outside_c.area() - self.inside_c.area() def perimeter(self): return self.outside_c.perimeter()+self.inside_c.perimeter()