[Devin]

import math

def numdigits(n): assert (n >= 0) and ((n % 1) == 0) if n < 10: return 1 return int(math.log10(n)) + 1

(not iterative, but it'll do :)

Nope, integers in Python are unbounded, and this will deliver wrong answers for "big enough" integers. Depending on the vagaries of your platform C's log10 implementation, it may even deliver a wrong answer for small n near an exact power of 10.

[Devin]

import math

def numdigits(n): assert (n >= 0) and ((n % 1) == 0) if n < 10: return 1 return int(math.log10(n)) + 1

(not iterative, but it'll do :)

Nope, integers in Python are unbounded, and this will deliver wrong answers for "big enough" integers. Depending on the vagaries of your platform C's log10 implementation, it may even deliver a wrong answer for small n near an exact power of 10.