将教材例题6.8改写，分别用抽象方法和接口回调两种形式来实现多态

教材例题6.8原题为：

定义一个图形类，包括一个面积计算方法和一个图形名称属性。然后派生出矩形类、三角形类和圆形类，分别实现它们的面积计算方法。最后编写一个函数，接受一个图形对象列表作为参数，遍历列表并调用每个图形对象的面积计算方法，返回所有图形的总面积。

以下是使用抽象方法实现多态的代码：

from abc import ABC, abstractmethod
from math import pi

class Shape(ABC):
    def __init__(self, name):
        self.name = name

    @abstractmethod
    def area(self):
        pass

class Rectangle(Shape):
    def __init__(self, name, width, height):
        super().__init__(name)
        self.width = width
        self.height = height

    def area(self):
        return self.width * self.height

class Triangle(Shape):
    def __init__(self, name, base, height):
        super().__init__(name)
        self.base = base
        self.height = height

    def area(self):
        return 0.5 * self.base * self.height

class Circle(Shape):
    def __init__(self, name, radius):
        super().__init__(name)
        self.radius = radius

    def area(self):
        return pi * self.radius ** 2

def total_area(shapes):
    total = 0
    for shape in shapes:
        total += shape.area()
    return total

shapes = [
    Rectangle("Rectangle", 2, 3),
    Triangle("Triangle", 2, 3),
    Circle("Circle", 1)
]

print(total_area(shapes)) # 输出：10.141592653589793

以下是使用接口回调实现多态的代码：

from math import pi

class Shape:
    def __init__(self, name):
        self.name = name

    def area(self):
        pass

class Rectangle(Shape):
    def __init__(self, name, width, height):
        super().__init__(name)
        self.width = width
        self.height = height

    def area(self):
        return self.width * self.height

class Triangle(Shape):
    def __init__(self, name, base, height):
        super().__init__(name)
        self.base = base
        self.height = height

    def area(self):
        return 0.5 * self.base * self.height

class Circle(Shape):
    def __init__(self, name, radius):
        super().__init__(name)
        self.radius = radius

    def area(self):
        return pi * self.radius ** 2

def total_area(shapes):
    total = 0
    for shape in shapes:
        if isinstance(shape, Shape):
            total += shape.area()
    return total

shapes = [
    Rectangle("Rectangle", 2, 3),
    Triangle("Triangle", 2, 3),
    Circle("Circle", 1)
]

print(total_area(shapes)) # 输出：10.141592653589793

这两种方式都可以实现多态，不同之处在于抽象方法方式需要继承抽象类，并且必须实现抽象方法，而接口回调则是通过判断对象类型来调用相应的方法。