Python 6b – While Loops

Learn condition-controlled iteration in Python with step-by-step examples and quick tasks to practise.

While Loops

Iteration lets programs repeat actions. In Python, while loops are condition controlled: the loop continues as long as the condition is True.

Simple while loop

This loop starts at 1 and increments until it exceeds 10:

number = 1
while number <= 10:
    print(number)
    number = number + 1

Task 1 – Countdown from 100

Create a while loop that prints each number from 100 down to 1:

number = 100
while number >= 1:
    print(number)
    number = number - 1

Inputs inside while loops

Use input inside the loop until a condition is met:

month = ""
while month != "July":
    month = input("Guess the month I'm thinking of: ")
print("Correct! It was July!")

Task 2 – Guess the colour

colour = ""
while colour.lower() != "yellow":
    colour = input("Guess the colour: ")
print("Correct! It was yellow!")

Task 3 – Integer trivia

correct_answer = 2008
year = 0
while year != correct_answer:
    year = int(input("Which year was the first Iron Man movie? "))
print("Correct! It was", correct_answer)

while True loops

A while True loop repeats indefinitely until you break:

while True:
    password = input("Enter the password: ")
    if password == "icecream21":
        print("Correct Password!")
        break

Counting attempts with while True

guesses = 0
while True:
    guesses += 1
    password = input("Enter the password: ")
    if password == "goat7":
        print("Correct Password! It took", guesses, "attempts!")
        break
    else:
        print("Incorrect. Try again!")

Using continue

Skip to the next iteration with continue:

total = 0
while True:
    choice = input("Type 1 to enter, 2 for total, and 3 to stop: ")
    if choice == "1":
        number = int(input("Enter a number: "))
        total += number
        continue
    elif choice == "2":
        print("The total is", total)
        continue
    elif choice == "3":
        break
print("Program finished.")

Task 4 – Guess the planet

guesses = 0
while True:
    guesses += 1
    planet = input("Enter a planet: ")
    if planet.lower() == "neptune":
        print("Correct! It was Neptune!")
        print("It took", guesses, "attempts.")
        break
    else:
        print("Incorrect guess, try again!")

Task 5 – Up to 100

Keep adding numbers until the total reaches 100 or more:

total = 0
while True:
    number = int(input("Enter a number: "))
    total += number
    print("The current total is:", total)
    if total >= 100:
        print("Over 100!")
        break
Tips:
  • Always update the variable inside the loop or you risk an infinite loop.
  • Use break to exit early; use continue to skip to the next iteration.
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