Beginner · While loops · 83 of 264
Reverse a number
Read a positive whole number and print its digits in reverse order, as a number (so 1200 becomes 21).
Input: a positive whole number. Output: the reversed number.
Examples
Input
1234
Output
4321
Input
1200
Output
21
Input
5
Output
5
One more test checks other inputs when you press Check.
Stuck? The idea behind 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.