converting between decimal and octal

Two functions to perform conversion between the decimal and octal representation of integers.

#! /usr/bin/env python

def decimal_to_octal(decimal_num):
 i, o = 1, 0
 while decimal_num > 0:
  mod = decimal_num % 8
  o += (i * mod)
  decimal_num /= 8
  i *= 10
 return o

def octal_to_decimal(octal_num):
 i, d = 0, 0
 while octal_num > 0:
  mod = octal_num % 10
  d += (mod * 8**i)
  octal_num /= 10
  i += 1
 return d

if __name__ == '__main__':
 originals = range(10)
 octals = [decimal_to_octal(d) for d in originals]
 decimals = [octal_to_decimal(b) for b in octals]
 assert originals == decimals
 print 'originals:', originals
 print 'octals:', octals
 print 'decimals:', decimals

Sample output below.