Abstract Classes

1from abc import ABC, abstractmethod
2
3class Shape(ABC):
4    @abstractmethod
5    def area(self):
6        pass
7
8    @abstractmethod
9    def perimeter(self):
10        pass
11
12    def describe(self):  # Concrete method
13        return f"Area: {self.area()}"
14
15# Cannot instantiate abstract class
16# shape = Shape()  # TypeError!
17
18class Rectangle(Shape):
19    def __init__(self, width, height):
20        self.width = width
21        self.height = height
22
23    def area(self):
24        return self.width * self.height
25
26    def perimeter(self):
27        return 2 * (self.width + self.height)
28
29rect = Rectangle(3, 4)
30print(rect.area())       # 12
31print(rect.describe())   # Area: 12