Some playing around with python

numeral2number.py

import re                                                                                                                           

subnums = [ ('cd',4*'c'),
    ('xl',4*'x'),
    ('iv',4*'i'),
    ('d',5*'c'),
    ('l',5*'x'),
    ('v',5*'i'),
    ('cm',9*'c'),
    ('xc',9*'x'),
    ('ix',9*'i')]
nums = [ ('m',1000), ('c',100), ('x', 10), ('i',1) ]

def cal(x):
  for (s, l) in subnums:
    x = x.replace(s, l)
  x = '+'.join(list(x))
  for (c, w) in nums:
    x = x.replace(c, str(w))
  if x == '': x = '0'
  return eval(x)

def ask():
  roman = raw_input('Input the Roman Number: ').lower()
  if (re.search("^m*?(d|cm|cd)?c*?(l|xc|xl)?x*?(ix|v|iv)?(i{1,3})?$",roman)):
    print "  The Roman number %s is actually %s" % (roman.upper(), cal(roman))
  else:
    print "  This is definately not a Roman Number."
    print "  Please pay attention."
    ask()

ask()