Python Classes and Objects

In the last tutorial, we learned about Python OOP. We know that Python also supports the concept of objects and classes.

An object is simply a collection of data (variables) and methods (functions). Similarly, a class is a blueprint for that object.

Before we learn about objects, let's first learn about classes in Python.

Python Classes

A class is considered a blueprint of objects.

We can think of the class as a sketch (prototype) of a house. It contains all the details about the floors, doors, windows, etc.

Based on these descriptions, we build the house; the house is the object.

Since many houses can be made from the same description, we can create many objects from a class.

Define Python Class

We use the class keyword to create a class in Python. For example,

class ClassName:
    # class definition 

Here, we have created a class named ClassName.

Let's see an example,

class Bike:
    name = ""
    gear = 0

Here,

1. Bike - the name of the class
2. name/gear - variables inside the class with default values "" and 0 respectively.

Note: The variables inside a class are called attributes.

Python Objects

An object is called an instance of a class.

Suppose Bike is a class then we can create objects like bike1, bike2, etc from the class.

Here's the syntax to create an object.

objectName = ClassName()

Let's see an example,

# create class
class Bike:
    name = ""
    gear = 0

# create objects of class
bike1 = Bike()

Here, bike1 is the object of the class. Now, we can use this object to access the class attributes.

Access Class Attributes Using Objects

We use the . notation to access the attributes of a class. For example,

# modify the name property
bike1.name = "Mountain Bike"

# access the gear property
bike1.gear

Here, we have used bike1.name and bike1.gear to change and access the value of name and gear attributes, respectively.

Example 1: Python Class and Objects

# define a class
class Bike:
    name = ""
    gear = 0

# create object of class
bike1 = Bike()

# access attributes and assign new values
bike1.gear = 11
bike1.name = "Mountain Bike"

print(f"Name: {bike1.name}, Gears: {bike1.gear} ")

Output

Name: Mountain Bike, Gears: 11

In the above example, we have defined the class named Bike with two attributes: name and gear.

We have also created an object bike1 of the class Bike.

Finally, we have accessed and modified the properties of an object using the . notation.

Create Multiple Objects of Python Class

We can also create multiple objects from a single class. For example,

# define a class
class Employee:
    # define a property
    employee_id = 0

# create two objects of the Employee class
employee1 = Employee()
employee2 = Employee()

# access property using employee1
employee1.employeeID = 1001
print(f"Employee ID: {employee1.employeeID}")

# access properties using employee2
employee2.employeeID = 1002
print(f"Employee ID: {employee2.employeeID}")

Output

Employee ID: 1001
Employee ID: 1002

In the above example, we have created two objects employee1 and employee2 of the Employee class.

Python Methods

We can also define a function inside a Python class. A Python function defined inside a class is called a method.

Let's see an example,

# create a class
class Room:
    length = 0.0
    breadth = 0.0
    
    # method to calculate area
    def calculate_area(self):
        print("Area of Room =", self.length * self.breadth)

# create object of Room class
study_room = Room()

# assign values to all the properties 
study_room.length = 42.5
study_room.breadth = 30.8

# access method inside class
study_room.calculate_area()

Output

Area of Room = 1309.0

In the above example, we have created a class named Room with:

1. Attributes: