Understanding construtor vs Attributes in python class

amitmund June 04, 2026

Constructor vs Attributes

The constructor and attributes are related, but they are not the same thing.

Think of it this way

Constructor = A Special Method

class Student:

    def __init__(self):
        self.name = "John"
        self.age = 20

Here:

def __init__(self):

is the constructor.

The constructor's job is to initialize (set up) the object when it is created.

Attributes = Data Stored in the Object

Inside the constructor:

self.name = "John"
self.age = 20

These are attributes (instance variables).

So:

Code	Meaning
`__init__()`	Constructor
`self.name`	Attribute
`self.age`	Attribute

Example 1: Fixed Values

class Student:

    def __init__(self):
        self.name = "John"
        self.age = 20

Create object:

s1 = Student()

Object becomes:

s1
├── name = John
└── age = 20

Every object gets the same values.

s1 = Student()
s2 = Student()

Both contain:

name = John
age = 20

Example 2: Values Passed from Outside

class Student:

    def __init__(self, name, age):
        self.name = name
        self.age = age

Create object:

s1 = Student("John", 20)

Python does:

Student.__init__(s1, "John", 20)

Inside constructor:

self.name = name

becomes:

s1.name = "John"

and

self.age = age

becomes:

s1.age = 20

Object:

s1
├── name = John
└── age = 20

Create another object:

s2 = Student("Alice", 22)

Object:

s2
├── name = Alice
└── age = 22

Now each object can have different values.

What's the Difference?

Version 1

class Student:

    def __init__(self):
        self.name = "John"
        self.age = 20

Values are hardcoded.

Every object gets:

John
20

Version 2

class Student:

    def __init__(self, name, age):
        self.name = name
        self.age = age

Values come from outside.

Student("John", 20)
Student("Alice", 22)
Student("Bob", 18)

Each object gets different data.

The Correct Terminology

❌ Incorrect

Passing values to attributes is called a constructor.

✅ Correct

__init__() is the constructor.

The constructor initializes attributes.

Values can be assigned to attributes inside the constructor.

Real-Life Analogy

Imagine a student admission form.

The form itself is the constructor.

def __init__(self, name, age):

The fields on the form are:

name
age

The stored information becomes attributes:

self.name
self.age

When someone fills:

Name = John
Age = 20

the constructor stores that data in the object.

One More Example

class Car:

    def __init__(self, brand, color):
        self.brand = brand
        self.color = color

Create:

c1 = Car("Toyota", "White")
c2 = Car("BMW", "Black")

Result:

c1
├── brand = Toyota
└── color = White

c2
├── brand = BMW
└── color = Black