The while loop

Learn conditional loops with while.

A while loop repeats a block as long as a condition is true:

count = 0
while count < 3:
    print(count)
    count += 1

This prints 0, 1, 2. The condition is checked at the start of each iteration; when it becomes False the loop ends.

In a while loop the condition must become False somewhere, or you get an infinite loop. count += 1 increments count each time.

while vs for

for runs for the length of a collection, while runs as long as a condition is true. Which to pick?

Example: waiting for the user to type 'quit' uses while.

Assign count = 0. Write while count < 3: print(count) and count += 1.

Show example solution

count = 0
while count < 3:
    print(count)
    count += 1

Complete the while condition

count = 0
while count ____ 3:
    print(count)
    count += 1

Show answer

count = 0
while count < 3:
    print(count)
    count += 1