from math import pi  # 从内置函数里面导入pi

 # 先定义一个圆类

 class Circle:

     def __init__(self,r):  # 初始化和self的创建，一个圆的属性就是半径

         self.r = r  # 赋值

     def area(self):  # 和圆相关的方法，计算圆的面积

         return self.r**2 * pi

     def perimeter(self):  # 和圆相关的方法，计算圆的面积

         return 2*pi*self.r

 # 再定义一个圆环类

 class Ring:

     def __init__(self,outside_r,inside_r):  # 初始化和self的创建，一个圆环的属性外半径和内半径

         self.outside_c = Circle(outside_r)  # 圆环的外半径通过圆类的半径赋值

         self.inside_c = Circle(inside_r)  # 圆环的内半径也是通过圆类的半径赋值

     def area(self):

         return self.outside_c.area() - self.inside_c.area()  # 直接引用圆类里面的计算面积的area方法，这里就涉及了组合的方法

     def perimeter(self):

         return self.outside_c.perimeter() + self.inside_c.perimeter()  # 直接引用圆类里面的计算周长的perimeter方法，这里就涉及了组合的方法

 ring = Ring(20,10)

 print(ring.area())  # 计算圆环的面积

 print(ring.perimeter())  # 计算圆环的周长

C:\Users\sku1-1\PycharmProjects\untitled\venv\Scripts\python.exe "C:/Users/sku1-1/PycharmProjects/untitled/day23  03 组合例子.py"

942.4777960769379

188.49555921538757

Process finished with exit code 0

class Teacher:

    def __init__(self,name,age,sex,birthday):

        self.name = name

        self.age = age

        self.sex = sex

        self.birthday = birthday

class Birthhday:

    def __init__(self,year,month,day):

        self.year = year

        self.month = month

        self.day = day

b = Birthhday(2000,5,1)  # 实例化

teacher = Teacher('丽丽',18,'女',b)  # 实例化

print(teacher.name)

print(teacher.birthday.year)  # 这里涉及了组合

print(teacher.birthday.day)  # 这里涉及了组合

C:\Users\sku1-1\PycharmProjects\untitled\venv\Scripts\python.exe "C:/Users/sku1-1/PycharmProjects/untitled/day23  03 组合例子.py"

丽丽

2000

1

Process finished with exit code 0

class 类名:

    静态属性='aaaa'

    def _init_(self):

        pass