Classes vs Objects

Part of the Object Oriented Programming section of Coddy's Python journey — lesson 3 of 64.

Classes and objects serve different purposes. A class is a blueprint, while an object is what you build from that blueprint.

Here is an example of a class:

class Dog:
	# shared by all dogs
    species = "Canis familiaris"

Now we can access the class attribute directly using Dog.species where Dog is the class name:

print(f"Class species: {Dog.species}")
# Class species: Canis familiaris

This accesses data from the class itself, not from any specific object.

Now lets explore how it works in objects. Create objects from the Dog class:

dog1 = Dog()
dog2 = Dog()

Objects can have individual attributes that classes cannot:

dog1.name = "Nicky"
dog1.breed = "Siberian Husky"

dog2.name = "Teemon" 
dog2.breed = "Shu'ali"

Compare what classes and objects can do:

print(f"Object 1: {dog1.name} is a {dog1.breed}")
print(f"Object 2: {dog2.name} is a {dog2.breed}")
print(f"Both share class attribute: {Dog.species}")

Output:

Object 1: Nicky is a Siberian Husky
Object 2: Teemon is a Shu'ali
Both share class attribute: Canis familiaris

Key Difference: The class Dog defines what all dogs have in common, while objects dog1 and dog2 represent specific, individual dogs with unique properties.

Challenge

Easy

Complete the code to create a Student class and two student objects. Add different names and grades to each student.

student.py: This is where you'll define your Student class.
driver.py: Main execution file that will import and use your Student class:
Complete the code to create a Student class and two student objects. Add different names and grades to each student.
student1 name is "Alice" with grade "A".
student2 name is "Bob" with grade "B".

Cheat sheet

A class is a blueprint that defines shared attributes and behaviors. An object is an instance created from that class with individual properties.

Define a class:

class Dog:
    # Class attribute - shared by all instances
    species = "Canis familiaris"

Access class attributes directly:

print(Dog.species)  # Canis familiaris

Create objects from a class:

dog1 = Dog()
dog2 = Dog()

Add individual attributes to objects:

dog1.name = "Nicky"
dog1.breed = "Siberian Husky"

dog2.name = "Teemon"
dog2.breed = "Shu'ali"

Objects can access both their individual attributes and class attributes:

print(f"{dog1.name} is a {dog1.breed}")  # Individual attributes
print(f"Species: {Dog.species}")          # Class attribute

Try it yourself

# Import the Student class
from student import Student

# TODO: Create two student objects


# TODO: Add attributes to student1


# TODO: Add attributes to student2


# Print student information
print(f"{student1.name} has grade {student1.grade} at {Student.school}")
print(f"{student2.name} has grade {student2.grade} at {Student.school}")