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🛠️ Functions·30 min·Intermediate🏆 Project
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Mini-Project: Calculator App

Build a working calculator!

Use functions with parameters and returns to build a calculator that can add, subtract, multiply, and divide!

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What we are learning

Time to build a real calculator! You will create functions for addition, subtraction, multiplication, and division. Each function takes two numbers as parameters and returns the result. Then you will build a menu so the user can choose an operation!

💡 Think of it like this:

Think of this project like building a mini robot calculator. Each math operation is a separate "skill" (function) the robot has. The user picks which skill to use, gives two numbers, and the robot does the rest!

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Why it matters

This project shows how functions with parameters and returns work together. It is a mini version of the calculator app on your phone — built from scratch with your own code!

Where you see this in real life:

  • ✓Calculator apps on phones and computers
  • ✓Spreadsheet formulas that do calculations
  • ✓Shopping apps that calculate totals and discounts
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By the end, you can:

  • 1.Write functions for each math operation
  • 2.Use parameters to pass in numbers
  • 3.Use return to send back results
  • 4.Build an interactive menu with input()
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New words

functionparameterreturninputfloat
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What operations should a calculator have? Write down all the math operations you can think of!
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Fun Fact!

The first mechanical calculator was built in 1642 by Blaise Pascal. It could only add and subtract. Your Python calculator can do much more!

🧮 Build a Calculator App!

Time to build a real calculator! You will create functions for each math operation, each taking two numbers as parameters and returning the result. Then you will build an interactive menu!

🏗️ Step 1: Math Functions

First, create a function for each operation. Each takes two numbers and returns the result.

🐍Step 1: Create math functions
main.py
● Output
Click ▶ Run to see the output!

🏗️ Step 2: The Full Calculator

Now add a menu so the user can choose an operation and enter numbers!

🐍Step 2: The complete calculator!
main.py
● Output
Click ▶ Run to see the output!

🚀 Challenge: Add More Features!

  • 🌟 Add a power function (num1 to the power of num2)
  • 🌟 Add a modulo (remainder) function
  • 🌟 Handle division by zero (show an error message)
  • 🌟 Let the user do multiple calculations in a loop
🐍Your turn — add more features!
main.py
● Output
Click ▶ Run to see the output!
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Amazing! You built a working calculator! 🎉 You used functions, parameters, returns, if/elif/else, and input all together!
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Quick Quiz!

+15 XP

Why do we use float() when getting numbers from input()?

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Finished the lesson? Click the button to mark it complete and earn XP!