Learn Python by Creating Your First Simple Calculator

Step by Step Guide for Beginners

Introduction

Are you new to programming and wondering how to start? Maybe you’ve heard about Python, but the idea of writing code seems intimidating. Don’t worry – you’re not alone!

Python is one of the most beginner-friendly programming languages, and it’s perfect for your first project. In this tutorial, we’ll guide you step by step to create your very own simple calculator. By the end, you’ll be able to perform addition, subtraction, multiplication, and division, while learning essential Python concepts like variables, user input, arithmetic operations, and error handling.

Even if you’ve never written a line of code before, this guide will help you succeed.

Step 1: Setting Up Python

Before writing any code, you need to set up Python on your computer. Python is available for Windows, Mac, and Linux.

Follow these steps:

Download Python
Visit python.org and download the latest version of Python (3.12 or newer).
Install a Code Editor
While you can use a simple text editor, an IDE makes coding much easier. Recommended options:
- VS Code (lightweight, free)
- PyCharm (feature-rich, beginner-friendly)
Test Python Installation
Open your terminal (or command prompt) and type: python --version You should see the version number. If you do, Python is installed and ready!

Tip: Don’t worry about warnings during installation. The important thing is that Python runs correctly.

Step 2: Writing Your First Python Program

Let’s start small. Open your IDE and create a new file called calculator.py. Then type:

print("Welcome to your simple Python calculator!")

Run the file. You should see:

Welcome to your simple Python calculator!

This is your first Python program! The print() function tells Python to display text. Think of it as making your computer talk to you.

Step 3: Taking User Input

Next, we want our calculator to get numbers from the user. For this, we use variables and the input() function.

num1 = float(input("Enter the first number: "))
num2 = float(input("Enter the second number: "))

Here’s what’s happening:

input() shows a prompt and waits for the user to type something.
float() converts the input to a number (with decimals) so we can do math.
num1 and num2 store these numbers for later calculations.

Tip: Without float(), Python would treat user input as text (strings), which can’t be used for math operations.

Step 4: Performing Calculations

Now it’s time for math! Python supports all basic arithmetic operations:

sum_result = num1 + num2
diff_result = num1 - num2
prod_result = num1 * num2
quot_result = num1 / num2

+ → addition
- → subtraction
* → multiplication
/ → division

To display the results:

print(f"Sum: {sum_result}")
print(f"Difference: {diff_result}")
print(f"Product: {prod_result}")
print(f"Quotient: {quot_result}")

If you enter 10 and 5, you’ll get:

Sum: 15.0
Difference: 5.0
Product: 50.0
Quotient: 2.0

You just created a working calculator! 🎉

Step 5: Adding Optional Features

Let’s make the calculator smarter and more user-friendly.

1. Let the User Choose an Operation

print("Select operation:")
print("1. Add")
print("2. Subtract")
print("3. Multiply")
print("4. Divide")

choice = input("Enter choice (1/2/3/4): ")

2. Handle Errors Gracefully

Sometimes users make mistakes. Python can handle them with try-except blocks:

try:
    num1 = float(input("Enter the first number: "))
    num2 = float(input("Enter the second number: "))
except ValueError:
    print("Oops! Please enter valid numbers.")

3. Perform Calculations Based on User Choice

if choice == '1':
    print(f"Result: {num1 + num2}")
elif choice == '2':
    print(f"Result: {num1 - num2}")
elif choice == '3':
    print(f"Result: {num1 * num2}")
elif choice == '4':
    print(f"Result: {num1 / num2}")
else:
    print("Invalid choice")

Now, the user can select which operation they want, and the calculator will respond correctly.