Inheritance

Definition: Inheritance is a core mechanism in Object-Oriented Programming (OOP) that allows a new class (called a child or subclass) to adopt and reuse the attributes and methods of an existing class (called a parent or superclass).

Why: Inheritance prevents code duplication. Instead of rewriting the exact same functions for different but related entities, you define the shared behavior once in a parent class, and let child classes automatically inherit it and add their own unique features.

The Hierarchy Relationship

• Parent Class (Superclass / Base Class): The existing class whose features are being passed down.
• Child Class (Subclass / Derived Class): The new class that inherits features from the parent class.

Example

# Parent Class
class Person:
    def speak(self):
        print("Hello")

# Child Class (Inherits from Person)
class Student(Person):
    pass

# Creating an instance of the Child Class
s = Student()

# The Student object can use methods from the Person class
s.speak()  # Output: Hello

Explanation

• Passing the Parent Class: By placing Person inside the parentheses during the definition of the student class (class Student(Person):), we establish the inheritance link.
• Reusing Logic: Even though the Student class is completely empty (using only the pass keyword), an object created from it (s) automatically gains access to the speak() method defined up in the Person class.

Extending Functionality (Method Overriding)

A child class isn't strictly locked into doing exactly what its parent does. If a child class needs to change how a specific method works, it can redefine that method with the same name. This is known as **Method Overriding**:

class Teacher(Person):
    # Overriding the parent's speak method
    def speak(self):
        print("Good morning, class!")

t = Teacher()
t.speak()  # Output: Good morning, class! (Uses the child's version, not the parent's)

Key Notes

• Inheritance represents an **"is-a" relationship**. For example, a Student is a Person, a Car is a Vehicle.
• To call a method from the parent class explicitly inside an overridden child method, you can use Python's built-in super() function (e.g., super().speak()).
• Python supports **Multiple Inheritance**, which means a child class can inherit features from more than one parent class at the same time (e.g., class Child(Parent1, Parent2):).