Object-Oriented Programming (OOPs)

Learn how Python uses classes and objects to organize programs into reusable, structured and maintainable code.

What is OOPs?

OOPs (Object-Oriented Programming) is a programming approach where a program is designed using objects and classes.

An object represents a real-world entity such as a student, employee, course or bank account. A class acts as a blueprint from which objects are created.

Python supports Object-Oriented Programming and provides important concepts such as:

• Classes and Objects
• Constructors
• Encapsulation
• Inheritance
• Polymorphism
• Abstraction

Why Do We Use OOPs?

OOPs helps developers build large applications in a structured and reusable way.

OOPs Concept Diagram

The following diagram shows the major concepts of Object-Oriented Programming in Python.

Example 🤓👀

Consider a training institute such as CIIT Training Institute.

We can represent a student using an object. The student can have data such as name, course and fees, along with behaviors such as displaying details.

class Student:

    def __init__(self, name, course, fees):
        self.name = name
        self.course = course
        self.fees = fees

    def display_details(self):
        print("Name:", self.name)
        print("Course:", self.course)
        print("Fees:", self.fees)


student1 = Student("Sam", "Java Full Stack", 35000)

student1.display_details()

Here, Student is the class and student1 is an object of that class.

Output

Name: Sam
Course: Java Full Stack
Fees: 35000

Class and Object

A class defines the structure and behavior of an entity, while an object is an actual instance of that class.

class Student:
    pass

student1 = Student()
student2 = Student()

In this example, Student is the class and student1 and student2 are objects.

Attributes and Methods

Objects generally contain two important types of members:

• Attributes: Store object data.
• Methods: Define actions or behavior.

class Student:

    def display(self):
        print("Student details")


student = Student()

student.display()

What is self?

In Python, self refers to the current object. It is used to access the attributes and methods of that particular object.

class Student:

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

    def show(self):
        print(self.name)


student = Student("Amit")

student.show()

Here, self.name stores the name inside the current student object.

Four Important OOPs Concepts

OOPs Program Flow

                                     Class
                                      ↓
                            Define Attributes & Methods
                                      ↓
                                 Create Object
                                      ↓
                                 Object Stores Data
                                      ↓
                                 Object Calls Methods
                                      ↓
                           Program Performs Required Operation

CIIT Example 📩🖥️

Suppose we want to manage students enrolled in different courses.

class Student:

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

    def show_course(self):
        print(self.name, "is learning", self.course)


student1 = Student("Priya", "Python Full Stack")
student2 = Student("Amit", ".NET Full Stack")

student1.show_course()
student2.show_course()

This approach keeps student data and student-related behavior together inside the Student class.

Priya is learning Python Full Stack
Amit is learning .NET Full Stack

Important Points to Remember

• Python supports Object-Oriented Programming.
• A class is a blueprint for creating objects.
• An object is an instance of a class.
• Attributes store data.
• Methods define behavior.
• self refers to the current object.
• The __init__() method is commonly used for object initialization.
• OOP concepts help create reusable and maintainable code.

Common Beginner Mistakes

• Forgetting the colon : after class definition.
• Incorrect indentation inside the class.
• Forgetting self in instance methods.
• Confusing a class with an object.
• Accessing an attribute before assigning it.

Interview Points

1. What is OOPs?
2. What is a class?
3. What is an object?
4. What is the difference between class and object?
5. What is the purpose of self in Python?
6. What is a constructor?
7. Explain encapsulation, inheritance, polymorphism and abstraction.

CIIT Practice Tasks

1. Create a Student class with name and age.
2. Create an Employee class with name, department and salary.
3. Create a Course class with course name and fees.
4. Create multiple objects from the same class.
5. Create a method that displays object information.