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Phase 3 🎮 — Control Flow

Topics: if-elif-else, for loops, while loops, break/continue, comparisons

Make your programs smart. Control flow lets your code make decisions, repeat tasks, and respond to different conditions.

🔄 Exercise Flow​

📚 Prerequisites​

Before starting these exercises, make sure you've read:

🔰 Starter: Number Guessing Game (Simple)​

Time: 12 minutes

Build a number guessing game where the computer picks a number and the user guesses it with hints.

Learning Objectives​

  • Use while loops for repeated execution
  • Use if-elif-else for conditional logic
  • Compare values with <, >, ==
  • Use break to exit a loop

Starter Code​

# Starter: Number Guessing Game
import random

secret = random.randint(1, 10)
guess = None

print("I'm thinking of a number between 1 and 10.")

# TODO: Use a while loop to keep asking until the user guesses correctly
# TODO: If guess < secret, print "Too low!"
# TODO: If guess > secret, print "Too high!"
# TODO: If guess == secret, print "Correct!" and break

# Your code here 👇

Expected Output​

I'm thinking of a number between 1 and 10.
Your guess: 5
Too low!
Your guess: 8
Too high!
Your guess: 7
Correct! 🎉

⭐ Medium: FizzBuzz With a Twist​

Time: 20 minutes

Implement FizzBuzz with extended rules, using both for and while loops, and allow the user to set custom rules.

Learning Objectives​

  • Use for loops with range()
  • Combine if-elif-else with modulo operator
  • Use continue to skip iterations
  • Accept and validate user configuration

Starter Code​

# Medium: FizzBuzz With a Twist

# TODO: Ask the user for two numbers (fizz_num, buzz_num)
# TODO: Ask the user for the max range (e.g., 50)
# TODO: Loop from 1 to max and print:
#   - "Fizz" if divisible by fizz_num
#   - "Buzz" if divisible by buzz_num
#   - "FizzBuzz" if divisible by both
#   - The number otherwise
# TODO: Skip numbers that contain the digit 7 (use continue)
# TODO: Stop early if the number is a multiple of both fizz_num and buzz_num squared

# Your code here 👇

Expected Output​

Enter Fizz number: 3
Enter Buzz number: 5
Enter max range: 30
1
2
Fizz
...
14
FizzBuzz (stopped early — 15 is 3*5)

🏆 Hard: Interactive Menu System​

Time: 35 minutes

Build a fully interactive restaurant menu system that uses nested conditionals, loops, and control flow to manage orders, apply discounts, and generate bills.

Learning Objectives​

  • Design nested if-elif-else structures for a multi-level menu
  • Use while loops for persistent interaction until the user quits
  • Combine break and continue for navigation flow
  • Handle invalid input gracefully
  • Build a complete interactive CLI application

Starter Code​

# Hard: Interactive Menu System

# Menu items with prices
menu = {
    "Burger": 5.99,
    "Pizza": 8.99,
    "Pasta": 7.49,
    "Salad": 4.99,
    "Fries": 2.99,
    "Soda": 1.99,
    "Water": 0.99
}

# TODO: Build an interactive system that:
#   1. Shows the menu and asks user to pick items (by name or number)
#   2. Lets user add items to an order (with quantities)
#   3. Shows the current order and total at any time
#   4. Applies discount rules:
#       - 10% off if order > $20
#       - Free drink if order > $30
#   5. Lets user remove items or change quantities
#   6. Generates a formatted bill when user types "done"
#   7. Handles invalid inputs without crashing

print("🍽️ Welcome to Python Diner!")
print("Type 'menu' to see items, 'order' to see your cart, 'done' to finish.\n")

order = {}

# Your code here 👇

Expected Output​

🍽️ Welcome to Python Diner!
Type 'menu' to see items, 'order' to see your cart, 'done' to finish.

> menu
1. Burger - $5.99
2. Pizza - $8.99
3. Pasta - $7.49
4. Salad - $4.99
5. Fries - $2.99
6. Soda - $1.99
7. Water - $0.99

> add Burger 2
2x Burger added ✅

> add Pizza 1
1x Pizza added ✅

> order
📋 Current Order:
   Burger x2 = $11.98
   Pizza x1 = $8.99
   Total: $20.97

> done
═══════════════════════
    PYTHON DINER BILL
═══════════════════════
Burger x2           $11.98
Pizza x1             $8.99
───────────────────────
Subtotal:           $20.97
Discount (10%):    -$2.10
───────────────────────
Total:              $18.87
───────────────────────
Thanks for dining! 🎉

💡 Tips for Success​

  • Indentation matters — Python uses indentation to determine which code is inside a block. Use 4 spaces consistently.
  • Test edge cases — What happens when the user enters a negative number? A string? Nothing?
  • Use while True for infinite loops that you break out of manually — it's clean and readable.
  • Combine conditions with and, or, not to write compact if statements.

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