self in Python

The “self” parameter represents the current object (instance) of the class.

It allows each object to keep track of its own data (attributes).
It must be the first parameter of any instance method inside a class (Python passes it automatically when you call a method).

Example: Without self. Imagine we define a method without self:

Python

class Student:
    def introduce():
        print("Hello, I am a student")

s1 = Student()
s1.introduce()   # ❌ TypeError (missing 1 required positional argument)

This fails because Python automatically passes the object (s1) to the method, but the method doesn’t accept it.

Example: With self.

Python

class Student:

    # Class attribute/variable
    Company = "Google"

    # Constructor
    def __init__(self, name, age):
        self.name = name   # self refers to the current object
        self.age = age

    # Method
    def introduce(self):
        print(f"My name is {self.name}, and I am {self.age} years old. Working in the company {self.Company}.")

# Create an instance of the class
s1 = Student("Ashish", 29)  # s1 is passed as self
s2 = Student("Katrina", 25) # s2 is passed as self

# change the class attribute for object s2
s2.Company = "Amazon"

# Call the method
s1.introduce()  
# Output: My name is Ashish, and I am 29 years old. Working in the company Google.

s2.introduce()
# Output: My name is Katrina, and I am 25 years old. Working in the company Amazon.

Here:
• When we call s1.introduce(), Python internally does:
• Student.introduce(s1)
• So, self = s1.
• When you call s2.introduce():
• Student.introduce(s2)
• So, self = s2.

Previous Next