What are abstract classes? Explain with suitable example.

Abstract Classes:

In object-oriented programming, an abstract class is a class that is declared abstract—it may or may not include abstract methods. Abstract classes cannot be instantiated, but they can be subclassed. Abstract methods are declared without an implementation (without braces, and followed by a semicolon), and must be implemented in derived classes.

Example:

Consider the following example in Python:

from abc import ABC, abstractmethod

class Animal(ABC):
    @abstractmethod
    def make_sound(self):
        pass

class Dog(Animal):
    def make_sound(self):
        print("Woof!")

class Cat(Animal):
    def make_sound(self):
        print("Meow!")

animal = Animal()  # Error: Can't instantiate abstract class Animal with abstract methods
dog = Dog()
dog.make_sound()  # Output: Woof!
cat = Cat()
cat.make_sound()  # Output: Meow!

In this example, the Animal class is declared as an abstract class with an abstract method make_sound. The Dog and Cat classes inherit from the Animal class and implement the make_sound method. We cannot instantiate the Animal class directly because it is abstract, but we can create objects of the Dog and Cat classes, which are concrete subclasses. When we call the make_sound method on the dog and cat objects, we get the expected outputs of "Woof!" and "Meow!", respectively.

Key Points:

• Abstract classes define a common interface for subclasses, ensuring that they all implement certain methods.
• Abstract methods have no implementation in the abstract class and must be implemented in subclasses.
• Abstract classes cannot be instantiated, but they serve as blueprints for creating concrete subclasses.
• Abstract classes promote code organization and maintainability by grouping related classes and methods together.
• They facilitate polymorphism, allowing objects of different subclasses to be treated uniformly.