Python Program to Define a Class and Create an Object

Introduction

Classes and objects are fundamental concepts in object-oriented programming (OOP). A class is a blueprint for creating objects (instances), providing initial values for state (member variables or properties) and implementations of behavior (member functions or methods). An object is an instance of a class, containing real data that the class blueprint defines.

This tutorial will guide you through creating a Python program that defines a simple class and creates an object from that class.

Example:

• Class Name: Car
• Attributes: brand, model, year
• Method: display_info (prints the car’s information)
• Program Output:

  Car: Toyota Corolla, Year: 2020
  

Problem Statement

Create a Python program that:

• Defines a class named Car.
• The class has attributes: brand, model, and year.
• The class has a method named display_info that prints the car’s information.
• Creates an object of the class and calls the method to display the car’s details.

Solution Steps

1. Define the Class: Use the class keyword to define a class named Car.
2. Add an Initialization Method: Define the __init__ method to initialize the object’s attributes.
3. Add a Method: Define a method named display_info to print the car’s details.
4. Create an Object: Instantiate an object of the Car class by passing appropriate arguments.
5. Call the Method: Call the display_info method on the object to display the car’s details.

Python Program

# Python Program to Define a Class and Create an Object
# Author: https://www.rameshfadatare.com/

# Step 1: Define the class
class Car:
    # Step 2: Define the initialization method
    def __init__(self, brand, model, year):
        self.brand = brand
        self.model = model
        self.year = year
    
    # Step 3: Define a method to display car information
    def display_info(self):
        print(f"Car: {self.brand} {self.model}, Year: {self.year}")

# Step 4: Create an object of the Car class
my_car = Car("Toyota", "Corolla", 2020)

# Step 5: Call the method to display car details
my_car.display_info()

Explanation

Step 1: Define the Class

• The Car class is defined using the class keyword. The class serves as a blueprint for creating car objects.

Step 2: Add an Initialization Method

• The __init__ method is a special method in Python classes that initializes new objects. It is called automatically when a new object is created.
• The __init__ method takes self (which refers to the current object) and other parameters (brand, model, year) to initialize the object’s attributes.

Step 3: Add a Method

• The display_info method is defined to print the car’s details. This method takes self as a parameter, allowing it to access the object’s attributes.

Step 4: Create an Object

• An object my_car is created by calling the Car class with specific arguments for brand, model, and year. This invokes the __init__ method to initialize the object’s attributes.

Step 5: Call the Method

• The display_info method is called on the my_car object to print the car’s details.

Output Example

Example Output:

Car: Toyota Corolla, Year: 2020

Additional Examples

Example 1: Define a Class with Multiple Methods

# Defining a class with multiple methods
class Student:
    def __init__(self, name, age, grade):
        self.name = name
        self.age = age
        self.grade = grade
    
    def display_info(self):
        print(f"Student: {self.name}, Age: {self.age}, Grade: {self.grade}")
    
    def is_pass(self):
        return self.grade >= 50

# Creating an object of the Student class
student = Student("Alice", 20, 85)

# Calling methods on the object
student.display_info()
print(f"Has passed: {student.is_pass()}")

Output:

Student: Alice, Age: 20, Grade: 85
Has passed: True

Example 2: Define a Class with Default Attribute Values

# Defining a class with default attribute values
class Book:
    def __init__(self, title, author, pages=100):
        self.title = title
        self.author = author
        self.pages = pages
    
    def display_info(self):
        print(f"Book: {self.title} by {self.author}, Pages: {self.pages}")

# Creating an object with default pages value
book1 = Book("1984", "George Orwell")

# Creating an object with custom pages value
book2 = Book("The Catcher in the Rye", "J.D. Salinger", 214)

# Displaying information about the books
book1.display_info()
book2.display_info()

Output:

Book: 1984 by George Orwell, Pages: 100
Book: The Catcher in the Rye by J.D. Salinger, Pages: 214

Example 3: Modify Object Attributes

# Modifying object attributes after creation
class Dog:
    def __init__(self, name, breed):
        self.name = name
        self.breed = breed
    
    def display_info(self):
        print(f"Dog: {self.name}, Breed: {self.breed}")

# Creating an object of the Dog class
dog = Dog("Buddy", "Golden Retriever")

# Displaying initial information
dog.display_info()

# Modifying the object's attributes
dog.name = "Max"
dog.breed = "Labrador Retriever"

# Displaying modified information
dog.display_info()

Output:

Dog: Buddy, Breed: Golden Retriever
Dog: Max, Breed: Labrador Retriever

Conclusion

This Python program demonstrates how to define a class, create an object, and interact with it using methods. Classes and objects are essential components of object-oriented programming, providing a way to structure code and create reusable components. Understanding how to define and use classes is crucial for writing organized, maintainable, and scalable Python programs.