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Python Class and Instance Attributes
Last Updated : May 03, 2025
In Python, class attributes and instance attributes are used to store data in objects. Class attributes are shared by all instances of the class, whereas instance attributes are specific to each object.
In this chapter, we will learn the difference between class and instance attributes with the help of examples.
Instance Attributes
Instance attributes are defined inside the __init__ method using self. These attributes are unique to each object.
Example
In this example, each student object has its own name and age.
# Defining a class with instance attributes
class Student:
def __init__(self, name, age):
self.name = name
self.age = age
# Creating objects
student1 = Student("Aarav", 20)
student2 = Student("Bhavya", 22)
# Accessing instance attributes
print(student1.name, student1.age)
print(student2.name, student2.age)
The output of the above code would be:
Aarav 20
Bhavya 22
Class Attributes
Class attributes are defined directly inside the class and outside any methods. They are shared among all instances of the class.
Example
In this example, all student objects share the same school attribute.
# Defining a class with a class attribute
class Student:
school = "Greenwood High" # Class attribute
def __init__(self, name):
self.name = name # Instance attribute
# Creating objects
student1 = Student("Charu")
student2 = Student("Deepak")
# Accessing class and instance attributes
print(student1.name, "-", student1.school)
print(student2.name, "-", student2.school)
The output of the above code would be:
Charu - Greenwood High
Deepak - Greenwood High
Modifying Instance Attributes
Instance attributes can be modified individually for each object without affecting others.
Example
In this example, we change the age of one student.
# Defining a class
class Student:
def __init__(self, name, age):
self.name = name
self.age = age
# Creating objects
student1 = Student("Esha", 21)
student2 = Student("Farhan", 23)
# Modifying instance attribute
student1.age = 22
# Displaying results
print(student1.name, student1.age)
print(student2.name, student2.age)
The output of the above code would be:
Esha 22
Farhan 23
Modifying Class Attributes
If you modify a class attribute using the class name, the change is reflected across all instances that have not overridden that attribute.
Example
In this example, we modify the class attribute school for all students.
# Defining a class
class Student:
school = "Greenwood High"
def __init__(self, name):
self.name = name
# Modifying class attribute
Student.school = "Sunrise Academy"
# Creating objects
student1 = Student("Gauri")
student2 = Student("Harsh")
# Displaying results
print(student1.name, "-", student1.school)
print(student2.name, "-", student2.school)
The output of the above code would be:
Gauri - Sunrise Academy
Harsh - Sunrise Academy
Overriding Class Attributes with Instance Attributes
If an attribute is set on an object with the same name as a class attribute, it overrides the class attribute for that object only.
Example
In this example, we override the class attribute for one object.
# Defining a class
class Student:
school = "Greenwood High"
def __init__(self, name):
self.name = name
# Creating objects
student1 = Student("Isha")
student2 = Student("Jay")
# Overriding class attribute for one instance
student1.school = "DPS Bangalore"
# Displaying results
print(student1.name, "-", student1.school)
print(student2.name, "-", student2.school)
The output of the above code would be:
Isha - DPS Bangalore
Jay - Greenwood High
Python Class and Instance Attributes Exercise
Select the correct option to complete each statement about class and instance attributes in Python.
- Attributes defined directly inside a class but outside any methods are called ___ attributes.
- Attributes that are unique to each object are called ___ attributes.
- To define an instance attribute, you typically assign it using ___ within the
__init__ method.
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