Python while loops and digit processing
A while loop checks its condition before every iteration, so its body may run zero times. A termination argument explains why the loop eventually stops.
Python
def digit_sum(number):
number = abs(number)
total = 0
while number > 0:
total += number % 10
number //= 10
return total
print(digit_sum(204))
assert digit_sum(0) == 0
assert digit_sum(-204) == 6