Python While Loops

while Loop Syntax

A while loop starts with the keyword while, followed by a condition and a colon. Python checks the condition before each pass; the moment it becomes False, the loop stops and execution continues after the loop.

count = 1
while count <= 5:
    print(count)
    count += 1

Using a Counter Variable

Most while loops rely on a counter variable that changes on each iteration, eventually making the condition False. Forgetting to update the counter is the most common beginner bug.

Infinite Loops

A loop written as while True: runs forever unless something inside it stops execution, usually with a break statement. Infinite loops are useful for programs that keep running until the user chooses to quit, like menus.

while True:
    answer = input("Type quit to stop: ")
    if answer == "quit":
        break
    print("You typed:", answer)

The while-else Clause

A while loop can have an optional else block. The else runs only if the loop finishes naturally because its condition became False — it is skipped if the loop exits early via break.

n = 1
while n < 4:
    print(n)
    n += 1
else:
    print("Loop finished normally")

Combining while with break

You can exit a while loop early with break, even if its condition is still True. This is common when searching for something and you want to stop as soon as it is found.

numbers = [4, 9, 15, 22, 30]
index = 0
while index < len(numbers):
    if numbers[index] == 15:
        print("Found at index", index)
        break
    index += 1