7-calculator.md

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Chapter 8: Simple Calculator Program

🚀 Open Notebook

📺 Video Tutorial

Let's code a simple python calculator! 🧮 (8:20)

📚 What You'll Learn

Build a functional calculator that performs basic mathematical operations!

🎯 Learning Objectives

• Combine user input with conditional statements
• Create a menu-driven program
• Handle different mathematical operations
• Validate user input
• Build a complete, useful program

📖 Concept Explanation

What is a Calculator Program?

A calculator program:

1. Asks the user what operation they want to perform
2. Gets the numbers to calculate
3. Performs the requested operation
4. Displays the result

Program Flow

1. Display available operators → 2. Get operator choice → 3. Get numbers → 
4. Check operator and calculate → 5. Display result

💡 Complete Program Breakdown

Step 1: Get Operator

:tags: [skip-execution]

operator = input("Enter operator (+, -, *, /, %): ")

Step 2: Get Numbers

:tags: [skip-execution]

number1 = float(input("Enter first number: "))
number2 = float(input("Enter second number: "))

Note: We use float() to handle both whole numbers and decimals

Step 3: Calculate Based on Operator

if operator == "+":
    result = number1 + number2
elif operator == "-":
    result = number1 - number2
# ... and so on

✍️ Practice Exercises

Exercise 1: Add Division by Zero Check

elif operator == "/":
    if number2 == 0:
        print("Error: Cannot divide by zero!")
    else:
        print(f"{number1} / {number2} = {number1 / number2}")

Exercise 2: Add More Operations

Add these operators:

• ** for exponentiation (power)
• // for floor division
• sqrt for square root

Exercise 3: Continuous Calculator

Make the calculator run in a loop until user chooses to exit:

while True:
    # calculator code here
    
    continue_calc = input("Another calculation? (yes/no): ")
    if continue_calc.lower() != "yes":
        break

Exercise 4: Calculator with Memory

Store the last result and allow using it in next calculation:

memory = 0
# Allow user to type "M" to use memory value

🔍 Enhancements

Enhancement 1: Better Output Formatting

if operator == "+":
    result = number1 + number2
    print(f"\n{number1} + {number2} = {result}")
    print(f"Result: {result:.2f}")  # 2 decimal places

Enhancement 2: Input Validation

valid_operators = ['+', '-', '*', '/', '%']
if operator not in valid_operators:
    print("Invalid operator!")

Enhancement 3: Try-Except for Error Handling

:tags: [skip-execution]

try:
    number1 = float(input("Enter first number: "))
    number2 = float(input("Enter second number: "))
except ValueError:
    print("Error: Please enter valid numbers!")

🎮 Advanced Calculator Features

Scientific Calculator

import math

if operator == "sqrt":
    result = math.sqrt(number1)
elif operator == "sin":
    result = math.sin(math.radians(number1))
elif operator == "cos":
    result = math.cos(math.radians(number1))

Calculator with History

history = []

# After each calculation:
history.append(f"{number1} {operator} {number2} = {result}")

# Display history:
for calc in history:
    print(calc)

📝 Common Operators Explained

Operator	Name	Example	Result
+	Addition	5 + 3	8
-	Subtraction	5 - 3	2
*	Multiplication	5 * 3	15
/	Division	6 / 2	3.0
%	Modulus	7 % 2	1
**	Power	2 ** 3	8
//	Floor Division	7 // 2	3

🚀 Challenge Projects

Challenge 1: Multi-Step Calculator

# Allow: 5 + 3 * 2 - 1
# Parse and calculate following order of operations

Challenge 2: Unit Converter

Add conversions:

• Temperature (C to F, F to C)
• Length (miles to km, km to miles)
• Weight (lbs to kg, kg to lbs)

Challenge 3: Percentage Calculator

# Calculate:
# - What is X% of Y?
# - X is what % of Y?
# - Percentage increase/decrease

Challenge 4: GUI Calculator

Use tkinter to create a calculator with buttons:

import tkinter as tk
# Create calculator with button interface

💻 Complete Enhanced Calculator

:tags: [skip-execution]

def calculator():
    print("=== Simple Calculator ===")
    print("Operations: +, -, *, /, %, **, //")
    
    operator = input("\nEnter operator: ")
    
    try:
        num1 = float(input("Enter first number: "))
        num2 = float(input("Enter second number: "))
        
        if operator == "+":
            result = num1 + num2
        elif operator == "-":
            result = num1 - num2
        elif operator == "*":
            result = num1 * num2
        elif operator == "/":
            if num2 == 0:
                print("Error: Division by zero!")
                return
            result = num1 / num2
        elif operator == "%":
            result = num1 % num2
        elif operator == "**":
            result = num1 ** num2
        elif operator == "//":
            result = num1 // num2
        else:
            print("Invalid operator!")
            return
        
        print(f"\n{num1} {operator} {num2} = {result}")
        print(f"Result: {result:.2f}")
        
    except ValueError:
        print("Error: Please enter valid numbers!")

# Run calculator
calculator()

🔗 Next Chapter

Continue to Chapter 9: Weight Converter to build another practical conversion program!