一文了解Python中NotImplementedError的作用

from abc import ABC, abstractmethod

class Shape(ABC):
    @abstractmethod
    def area(self):
        raise NotImplementedError("子类必须实现这个方法")

class Circle(Shape):
    def __init__(self, radius):
        self.radius = radius
    
    def area(self):
        return 3.14 * self.radius ** 2

class Square(Shape):
    def __init__(self, side):
        self.side = side
    
    def area(self):
        return self.side ** 2

# 正确使用
circle = Circle(5)
print(circle.area())  # 输出圆的面积

square = Square(4)
print(square.area())  # 输出正方形的面积

# 错误使用
shape = Shape()  # 这里会抛出TypeError，因为Shape是抽象基类，不能直接实例化
print(shape.area())  # 这行代码不会执行，因为上面已经抛出了异常

from abc import ABC, abstractmethod

class DataStore(ABC):
    @abstractmethod
    def save_data(self, data):
        raise NotImplementedError("子类必须实现这个方法以保存数据")
    
    @abstractmethod
    def load_data(self):
        raise NotImplementedError("子类必须实现这个方法以加载数据")

class FileDataStore(DataStore):
    def __init__(self, filename):
        self.filename = filename
    
    def save_data(self, data):
        with open(self.filename, 'w') as file:
            file.write(data)
    
    def load_data(self):
        with open(self.filename, 'r') as file:
            return file.read()

# 使用自定义接口
store = FileDataStore('data.txt')
store.save_data('Hello, world!')
data = store.load_data()
print(data)  # 输出: Hello, world!