Task_14_while_loops.md

Task 14 - While loops

A while loop keeps running as long as its condition stays True. If you forget to change the condition inside the loop, it will run forever.

---

Demo 1 - Countdown

number = 10

while number >= 0:          # loop stops when number is -1
    print(number)
    number -= 1             # move toward the stopping point

print("Blast-off!")

• The loop prints 10 9 8 … 0.
• Updating number (number -= 1) is crucial; otherwise the test number >= 0 would never become False.

---

Demo 2 - Echo until the user quits

command = ""

while command.lower() != "quit":
    command = input("> ")
    print("ECHO", command)

• .lower() lets the user type quit, Quit, or QUIT.
• The loop ends only when the typed word equals "quit".

---

Your exercise

1. Create a file called Task_14.py.

2. Part A - Countdown

   • Ask the user for a starting number with input("Start countdown at: ") and convert it to int.
   • Use a while loop to count down to 0, printing each number on its own line.
   • After the loop, print "Launch!".

3. Part B - Password gate

   • Set password = "letmein".
   • Use a while loop that keeps asking input("Password: ") until the user enters the correct password or types "quit".
   • If the user types the right password, print "Access granted" and stop the loop with break.
   • If they type "quit", print "Goodbye" and stop the loop.
   • For any other input, print "Incorrect - try again" and continue looping.

Run the script and test each path: successful login, quitting, and repeated wrong attempts - to see how while, break, and a changing condition control program flow.