In this tutorial, we’ll build a simple Python calculator that performs basic arithmetic operations like addition, subtraction, multiplication, and division.

Table of Contents:

1. Introduction

2. Step 1: Define the Functions

3. Step 2: Take User Input

4. Step 3: Perform the Operation and Show the Result

5. Step 4: Add a Loop to Repeat the Calculator

6. Conclusion

---

Introduction

Python is great for building basic tools, and a calculator is a perfect starting project for any beginner. We'll be using Python’s built-in functions, and you’ll learn how to handle user input, write functions, and manage control flow.

---

Step 1: Define the Functions

Let's start by defining functions for each operation we want our calculator to perform.

Syntax for function definition:

def function_name():
    codes come here

def add(x, y):    
    return x + y

def subtract(x, y):
    return x - y

def multiply(x, y):
    return x * y

def divide(x, y):
    if y == 0:
        return "Error: Cannot divide by zero."
    return x / y

Step 2: Take User Input

Now, let’s take input from the user. We’ll ask the user to select an operation and input two numbers.

Syntax for taking user input:

variable = input("message you want to display to the user")

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

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

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

Step 3: Perform the Operation and Show the Result

We can now use if-else statements to perform the selected operation and show the result.

Syntax for an if*-*else statement in python:

if condition: 
    # Code to execute if the condition is True 
else: 
    # Code to execute if the condition is False

if choice == '1':
    result = add(num1, num2)
    print("Result:", result)

elif choice == '2':
    result = subtract(num1, num2)
    print("Result:", result)

elif choice == '3':
    result = multiply(num1, num2)
    print("Result:", result)

elif choice == '4':
    result = divide(num1, num2)
    print("Result:", result)

else:
    print("Invalid input. Please select a valid operation.")

Step 4: Add a Loop to Repeat the Calculator

To make the calculator usable multiple times without restarting the program, let’s add a loop that allows the user to continue using the calculator until they decide to quit.

while True:
    print("\nSelect operation:")
    print("1. Add")
    print("2. Subtract")
    print("3. Multiply")
    print("4. Divide")
    print("5. Exit")

    choice = input("Enter choice (1/2/3/4/5): ")

    if choice == '5':
        print("Exiting calculator. Goodbye!")
        break

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

    if choice == '1':
        print("Result:", add(num1, num2))
    elif choice == '2':
        print("Result:", subtract(num1, num2))
    elif choice == '3':
        print("Result:", multiply(num1, num2))
    elif choice == '4':
        print("Result:", divide(num1, num2))
    else:
        print("Invalid input. Please select a valid operation.")

Conclusion

Congrats! 🎉 You've just built a simple Python calculator that can perform basic arithmetic operations. This project teaches you valuable skills like handling user input, writing functions, and using control flow in Python.

---

What’s Next?

Now that you've created this basic calculator, here are some ideas to extend the project:

• Add more advanced operations (modulus, exponentiation, square root)

• Build a graphical user interface (GUI) for the calculator using Tkinter

• Turn the calculator into a web app with Flask or Django

---

Happy coding! 👨‍💻💡