Explain abstract base classes with suitable example.

Abstract Base Classes (ABCs)

Abstract base classes (ABCs) are a way to define a common interface for a set of related classes. They are used to establish a contract between different parts of your code, ensuring that certain methods and attributes are implemented in all conforming subclasses. ABCs are particularly useful when working with inheritance and polymorphism, as they allow you to create a base class that specifies the required behavior for its subclasses without providing a complete implementation.

Key Features of Abstract Base Classes

• Define a common interface for a set of related classes.
• Ensure that certain methods and attributes are implemented in all conforming subclasses.
• Promote code reusability and maintainability.
• Facilitate the use of polymorphism.

Creating an Abstract Base Class

To create an abstract base class in Python, you use the abc module. The following code shows an example of an abstract base class called Shape:

from abc import ABC, abstractmethod

class Shape(ABC):

    @abstractmethod
    def area(self):
        pass

    @abstractmethod
    def perimeter(self):
        pass

In this example, the Shape class defines two abstract methods: area() and perimeter(). These methods are marked as abstract using the @abstractmethod decorator, indicating that they must be implemented in any subclasses of Shape.

Creating Subclasses of an Abstract Base Class

To create a subclass of an abstract base class, you must implement all of the abstract methods defined in the base class. For example, the following code shows a subclass called Rectangle that extends the Shape class:

class Rectangle(Shape):

    def __init__(self, width, height):
        self.width = width
        self.height = height

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

    def perimeter(self):
        return 2 * (self.width + self.height)

In this example, the Rectangle class implements the abstract methods area() and perimeter() from the Shape class. This allows the Rectangle class to be used in place of any other class that conforms to the Shape interface.

Benefits of Using Abstract Base Classes

There are several benefits to using abstract base classes:

• Code Reusability: ABCs allow you to define a common interface for a set of related classes, which can lead to code reusability. For example, if you have multiple classes that represent different shapes, you can define an abstract base class called Shape that specifies the common methods and attributes for all shapes. This allows you to write code that operates on any type of shape without having to worry about the specific implementation details of each shape class.
• Maintainability: ABCs can improve the maintainability of your code by enforcing certain constraints on your subclasses. For example, if you have an abstract base class that specifies certain methods and attributes, you can be sure that all subclasses of that base class will implement those methods and attributes. This makes it easier to reason about the behavior of your code and to maintain it over time.
• Polymorphism: ABCs facilitate the use of polymorphism, which is the ability for objects of different classes to respond to the same method call in different ways. For example, if you have an abstract base class called Shape that defines an area() method, you can create subclasses of Shape that implement the area() method in different ways. This allows you to write code that operates on any type of shape without having to worry about the specific implementation details of each shape class.

Conclusion

Abstract base classes are a powerful tool for designing and organizing Python code. They allow you to define a common interface for a set of related classes, promote code reusability, improve maintainability, and facilitate the use of polymorphism.