What init and self do in Python?

Python __init__ and self keywords: Here, we are going to learn about the __init__ and self keywords in Python with examples. By Sapna Deraje Radhakrishna Last updated : December 16, 2023

What are init and self in Python?

The __init__ and self are two keywords in Python, which performs a vital role in the application.

To begin with, it is important to understand the concept of class and object.

Class

In Object-oriented programming, a class is a blueprint for creating objects of a particular data structure, provisioning the initial values for the state, and implementation of a behavior.

The user-defined objects are created using the class keyword.

Object

It is a basic unit of Object-Oriented Programming and each object is an instance of a particular class or subclass with class's methods or procedures and data variables.

With the above understanding,

Python init

__init__ is a reserved method in python classes. It is used to create an object of a class, something like a constructor in Java. This method when called creates an object of the class and it allows the class to initialize the attributes of the class.

Example usage of Python init

# A Sample class with init method 
class Country:     
    # init method or constructor 
    def __init__(self, name): 
        self.name = name 
    
    # Sample Method 
    def hello(self): 
        print('Hello, my name is', self.name) 
    
c = Country('India') 
c.hello()

Output

Hello, my name is India

In the above example, the line c = Country('India') invokes the method __init__ and creates an object c, which can then further invoke the method hello().

Python self

The word self is used to represent the instance of the class. Using self, the attributes and the methods of the class can be accessed.

Example usage of Python self

class Country:     
    # init method or constructor 
    def __init__(self, name): 
        self.name = name 
    
    # Sample Method 
    def hello(self): 
        print('Hello, my name is', self.name)