Python while loops

A while loop repeats as long as its condition is true: use it when you don't know in advance how many times.

Something inside the loop must change, so the condition becomes false in the end.

n = int(input())
digits = 0
while n > 0:
    n //= 10
    digits += 1
print(digits)

Watch for: If nothing in the loop changes the condition, it never ends and the program is stopped after a few seconds.