Master Python’s __init__: How Constructors Initialize Your Objects

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1. Introduction

Recently a question was asked in a Python group about the purpose of the __init__ constructor and whether other methods can retrieve its parameters.

2. Explanation

In object‑oriented programming, a constructor is a special method automatically called when a new class instance is created. Its main role is to initialize the object's state by setting initial attribute values.

In Python the constructor is named __init__ and receives the first parameter self, which references the current instance. Using self you can access and set attributes and call other methods.

Below is a simple class definition that includes a constructor:

class MyClass:
    def __init__(self, param1, param2):
        self.param1 = param1  # assign parameter to attribute
        self.param2 = param2  # other initialization

    def my_method(self):
        # this method can use the object's attributes
        return self.param1 + self.param2

When you create an instance of MyClass you can pass the two parameters, which are stored as the object's state:

# Create an instance and pass arguments
my_instance = MyClass(10, 20)

# Call a method that uses the initialized attributes
result = my_instance.my_method()  # result is 30

The method my_method can directly access the attributes set in __init__, demonstrating how constructors allow you to define initial values that other methods can use.

3. Summary

This article explained the purpose of Python's __init__ constructor, showed how it initializes object attributes, and provided example code illustrating its use.