In Python, the self keyword represents the instance of the class and is used to access variables and methods that belong to that specific object.

It allows each object to maintain its own state and helps differentiate between instance variables and local variables.

🧩 Example 1: Basic Use of self

class Student:
    def __init__(self, name, age):
        self.name = name   # instance variable
        self.age = age     # instance variable

    def show(self):
        print("Name:", self.name)
        print("Age:", self.age)

s1 = Student("Dheeraj", 24)
s1.show()

class Student:
    def __init__(self, name, age):
        self.name = name   # instance variable
        self.age = age     # instance variable

    def show(self):
        print("Name:", self.name)
        print("Age:", self.age)

s1 = Student("Dheeraj", 24)
s1.show()

Output:

Name: Dheeraj
Age: 24

Name: Dheeraj
Age: 24

Explanation:

• self.name and self.age refer to the object’s own data.
• When s1.show() is called, Python automatically passes the object s1 as the first argument to the show() method.

🧩 Example 2: Without Using self (Incorrect Example)

class Student:
    def __init__(name, age):  # ❌ Missing 'self' convention
        name = name
        age = age

s = Student("Dheeraj", 24)  # Will raise an error

class Student:
    def __init__(name, age):  # ❌ Missing 'self' convention
        name = name
        age = age

s = Student("Dheeraj", 24)  # Will raise an error

Output:

TypeError: Student.__init__() takes 2 positional arguments but 3 were given

TypeError: Student.__init__() takes 2 positional arguments but 3 were given

Explanation:
Without self, Python does not know which instance the attributes belong to.

🧩 Example 3: Using self to Access Other Methods

class Calculator:
    def __init__(self, num):
        self.num = num

    def square(self):
        return self.num ** 2

    def cube(self):
        return self.num ** 3

    def display(self):
        print("Square:", self.square())
        print("Cube:", self.cube())

calc = Calculator(3)
calc.display()

class Calculator:
    def __init__(self, num):
        self.num = num

    def square(self):
        return self.num ** 2

    def cube(self):
        return self.num ** 3

    def display(self):
        print("Square:", self.square())
        print("Cube:", self.cube())

calc = Calculator(3)
calc.display()

Output:

Square: 9
Cube: 27

Square: 9
Cube: 27

🧩 Example 4: self Refers to Each Instance Separately

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

dog1 = Dog("Buddy")
dog2 = Dog("Max")

print(dog1.name)
print(dog2.name)

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

dog1 = Dog("Buddy")
dog2 = Dog("Max")

print(dog1.name)
print(dog2.name)

Output:

Buddy
Max

Buddy
Max

Each object (dog1, dog2) has its own copy of the variable name because of self.

🔹 In Summary

• self refers to the instance of the class and helps access instance attributes and methods.
• It is automatically passed when calling instance methods.
• It ensures each object maintains its own state.
• Although you can use another name instead of self, it is a Python convention and should always be used for clarity and consistency.