定义一个矩形类，拥有属性：长、宽 拥有方法：求周长、求面积
class Rectangle: def __init__(self, length, width): self.length = length self.width = width def perimeter(self): return (self.width + self.length) * 2 def area(self): return self.length * self.width re1 = Rectangle(100, 20) print(re1.area(), re1.perimeter())定义一个二维点类，拥有属性：x坐标、y坐标 拥有方法：求当前点到另外一个点的距离
class Point: def __init__(self, x, y): self.x = x self.y = y def distance(self, point): return ((self.x - point.x) ** 2 + (self.y - point.y) ** 2) ** 0.5定义一个圆类，拥有属性：半径、圆心 拥有方法：求圆的周长和面积、判断当前圆和另一个圆是否外切
import math class Circle: class Point: def __init__(self, x, y): self.x = x self.y = y def __init__(self, r, point): self.r = r self.point = point def perimeter(self): return 2 * math.pi * self.r def area(self): return math.pi * self.r ** 2 def exterior_contact(self, other): if self.r + other.r == ((self.point.x - other.point.x) ** 2 + (self.point.y - other.point.y) ** 2) ** 0.5: return '是外切' else: return '不是外切' c1 = Circle(1, Circle.Point(0, 0)) c2 = Circle(1, Circle.Point(0, 0)) print(c2.exterior_contact(c1))定义一个线段类，拥有属性：起点和终点， 拥有方法：获取线段的长度
class Segment: class Point: def __init__(self, x, y): self.x = x self.y = y def __init__(self, point1, point2): self.start = point1 self.end = point2 def length(self): return ((self.start.x - self.end.x) ** 2 + (self.start.y - self.end.y) ** 2) ** 0.5 l1 = Segment(Segment.Point(1, 2), Segment.Point(1, 3)) print(l1.length())定义一个狗类和一个人类：
狗拥有属性：姓名、性别和品种 拥有方法：叫唤
人类拥有属性：姓名、年龄、狗 拥有方法：遛狗
class Dog: def __init__(self, name, sex, var): self.name = name self.sex = sex self.var = var def call(self): return f'{self.name}在叫唤' class Person: def __init__(self, name, age, dog): self.name = name self.age = age self.dog = dog def walk_dog(self): return f'{self.name}在遛{self.dog.name}' p1 = Person('小明', 18, Dog('大黄', '雄性', '土狗')) print(p1.walk_dog())