9 4 1 Single Inheritance Explained

Key Concepts

Single inheritance in Python involves several key concepts:

• Superclass and Subclass
• Inheriting Attributes and Methods
• Overriding Methods
• Accessing Superclass Methods

1. Superclass and Subclass

In single inheritance, a subclass inherits from a single superclass. The superclass is the class being inherited from, and the subclass is the class that inherits.

Example:

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

    def speak(self):
        return "Animal sound"

class Dog(Animal):
    pass

my_dog = Dog("Buddy")
print(my_dog.name)  # Output: Buddy
print(my_dog.speak())  # Output: Animal sound
    

Analogy: Think of the superclass as a parent and the subclass as a child who inherits traits from the parent.

2. Inheriting Attributes and Methods

The subclass inherits all attributes and methods from the superclass. This allows the subclass to reuse and extend the functionality of the superclass.

Example:

class Vehicle:
    def __init__(self, make, model):
        self.make = make
        self.model = model

    def start(self):
        return "Engine started!"

class Car(Vehicle):
    pass

my_car = Car("Toyota", "Camry")
print(my_car.make)  # Output: Toyota
print(my_car.start())  # Output: Engine started!
    

Analogy: Think of the subclass as a tool that comes with a set of pre-built features from the superclass.

3. Overriding Methods

The subclass can override methods inherited from the superclass. This allows the subclass to provide its own implementation of the method.

Example:

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

    def speak(self):
        return "Animal sound"

class Dog(Animal):
    def speak(self):
        return "Woof!"

my_dog = Dog("Buddy")
print(my_dog.name)  # Output: Buddy
print(my_dog.speak())  # Output: Woof!
    

Analogy: Think of overriding as customizing a recipe while keeping the basic ingredients the same.

4. Accessing Superclass Methods

The subclass can access methods from the superclass using the super() function. This is useful when you want to extend the functionality of the superclass method.

Example:

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

    def speak(self):
        return "Animal sound"

class Dog(Animal):
    def speak(self):
        return super().speak() + " Woof!"

my_dog = Dog("Buddy")
print(my_dog.name)  # Output: Buddy
print(my_dog.speak())  # Output: Animal sound Woof!
    

Analogy: Think of super() as a way to call the parent's version of a method before adding your own twist.

Putting It All Together

By understanding and using these concepts effectively, you can create more organized and reusable code using single inheritance in Python.

Example:

class Vehicle:
    def __init__(self, make, model):
        self.make = make
        self.model = model

    def start(self):
        return "Engine started!"

class Car(Vehicle):
    def start(self):
        return super().start() + " Car engine started!"

my_car = Car("Toyota", "Camry")
print(my_car.make)  # Output: Toyota
print(my_car.start())  # Output: Engine started! Car engine started!