First Python Project: A Simple Calculator

Congratulations on getting started with Python! Let’s now build your first project: a Simple Calculator. This project will teach you how to interact with users, perform basic calculations, and organize your code into functions.

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Project Overview

You will create a Python program that:

• Prompts the user to input two numbers.
• Asks the user to select an operation: addition, subtraction, multiplication, or division.
• Displays the result of the selected operation.

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Step 1: Plan Your Project

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Step 2: Write the Code

Open your editor and create a new file named calculator.py. Add the following code:

# Simple Calculator in Python

def add(a, b):
    return a + b

def subtract(a, b):
    return a - b

def multiply(a, b):
    return a * b

def divide(a, b):
    if b == 0:
        return "Error: Division by zero is not allowed."
    return a / b

print("Welcome to the Simple Calculator!")
print("Select an operation:")
print("1. Addition")
print("2. Subtraction")
print("3. Multiplication")
print("4. Division")

choice = input("Enter the number of your choice (1/2/3/4): ")

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

if choice == '1':
    print("The result is:", add(num1, num2))
elif choice == '2':
    print("The result is:", subtract(num1, num2))
elif choice == '3':
    print("The result is:", multiply(num1, num2))
elif choice == '4':
    print("The result is:", divide(num1, num2))
else:
    print("Invalid choice. Please run the program again.")

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Step 3: Run the Program

1. Save the file as calculator.py.
2. Run the program:

   python calculator.py
   

3. Follow the on-screen instructions to perform calculations.

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How It Works

1. Functions:
   Each mathematical operation (add, subtract, multiply, divide) is defined in a separate function for modularity.

2. Input and Output:

   • The program takes input from the user using the input function.
   • It converts the input to float to handle decimal numbers.

3. Decision Making:
   The program uses if-elif-else statements to perform the operation based on the user's choice.