Lab Practical Exercise: Python Abstract Classes and ABC Module (Step-by-Step)

Lab Practical Exercise: Python Abstract Classes and ABC Module (Step-by-Step)

Lab Title

Working with Abstract Classes and ABC in Python

Objective

By completing this lab, students will learn:

• What an abstract class is
• How to import and use the abc module
• How to create abstract methods
• How to inherit from an abstract class
• How to implement abstract methods in child classes
• How abstract classes improve program structure

Pre-Lab Requirements

Before starting, students should know:

• Python classes and objects
• Constructors __init__()
• Inheritance
• Functions and methods

Software Required

• Python installed on computer
• VS Code / PyCharm / IDLE / Jupyter Notebook

Important Theory

What is an Abstract Class?

An abstract class is a parent class used as a blueprint. It contains one or more methods that must be completed in child classes.

Why Use It?

Use abstract classes when multiple classes should follow the same structure.

Example:

• Animal classes must have sound()
• Shape classes must have area()
• Employee classes must have salary()

Step 1: Create Python File

Create a new Python file:

lab_abstract.py

Step 2: Import Required Module

At the top of the file, import:

ABC
abstractmethod

from Python abc module.

Step 3: Create Parent Abstract Class

Create a class named:

Animal

Make this class inherit from ABC.

Step 4: Create Abstract Method

Inside Animal class, create a method named:

sound()

Rules:

• Use @abstractmethod
• Keep method body empty using pass

Step 5: Create Child Class Dog

Create a new class:

Dog

This class must inherit from Animal.

Now override sound() method.

Inside method display:

Dog barks

Step 6: Create Child Class Cat

Create another child class:

Cat

This class also inherits from Animal.

Override sound() method.

Inside method display:

Cat meows

Step 7: Create Objects

Create objects of:

• Dog
• Cat

Store in variables.

Example:

d
c

Step 8: Call Methods

Call sound() method using both objects.

Expected behavior:

• Dog object prints barking sound
• Cat object prints meow sound

Step 9: Run Program

Run the file and observe output.

Step 10: Test Important Rule

Try creating object of parent abstract class:

Animal()

Observe the error message.

Write in notebook:

Why did the error occur?

Practical Exercise 2: Shape Program

Task

Create abstract class:

Shape

Create abstract method:

area()

Create Child Classes

Rectangle

Use constructor to receive:

• length
• width

Area formula:

length × width

Circle

Use constructor to receive:

• radius

Area formula:

Use math.pi

Final Steps

• Create object of Rectangle
• Create object of Circle
• Print both areas

Practical Exercise 3: Employee Salary System

Task

Create abstract class:

Employee

Create abstract method:

```python id=”q9qkq4” salary()

---

## Create Child Classes

### FullTimeEmployee

Return fixed salary.

### PartTimeEmployee

Return smaller salary.

---

## Final Steps

* Create both objects
* Print salaries

---

# Challenge Exercise

Create abstract class:

```python
Vehicle

Abstract method:

start()

Create child classes:

• Car
• Bike
• Bus

Each should print different start message.

Output Format Example

Dog barks
Cat meows
Rectangle Area: ...
Circle Area: ...
Full Time Salary: ...

Lab Report Questions

1. What is abstract class?
2. Why do we use ABC?
3. What is @abstractmethod?
4. Can we create object of abstract class?
5. What happens if child class does not define abstract method?

Submission Requirements

Students must submit:

• Python file
• Screenshot of output
• Answers of lab questions

Teacher Evaluation Rubric