converting between decimal and hexadecimal

Two functions for converting between decimal and hexadecimal.

def decimal_to_hexadecimal(decimal_num):
 if decimal_num == 0:
  return '0'
 hexvals = map(str, range(10)) + ['A', 'B', 'C', 'D', 'E', 'F']
 h = ''
 while decimal_num > 0:
  mod = decimal_num % 16
  h = hexvals[mod] + h
  decimal_num /= 16
 return h

def hexadecimal_to_decimal(hex_num):
 hexvals = map(str, range(10)) + ['A', 'B', 'C', 'D', 'E', 'F']
 i, d = len(hex_num)-1, 0
 while i >= 0:
  #print i
  d = d + hexvals.index(hex_num[i]) * 16**(len(hex_num)-1-i)
  i -= 1
 return d

def test_hex():
 originals = range(20)
 hexes = [decimal_to_hexadecimal(d) for d in originals]
 decimals = [hexadecimal_to_decimal(b) for b in hexes]
 assert originals == decimals
 print 'originals:', originals
 print 'hexes:', hexes
 print 'decimals:', decimals

if __name__ == '__main__':
 test_hex()

Below is some sample output.