getRomanNum('MDCCCLXXXVIII')

def getRomanNum(RomanStr):
 """Roman numerals will be converted into digital,RomanStr is a RomanString"""
   import re
   if re.search('^M{0,4}(CM|CD|D?C{0,3})(XC|XL|L?X{0,3})(IX|IV|V?I{0,3})$',RomanStr)!=None:
     NumDic = {"pattern":"","retNum":0}
     RomanPattern = {
       "0":('','','','M'),
       "1":('CM','CD','D','C',100),
       "2":('XC','XL','L','X',10),
       "3":('IX','IV','V','I',1)
       }
     i = 3
     NumItems = sorted(RomanPattern.items())
     for RomanItem in NumItems:
       if RomanItem[0] != '0':
         patstr = NumDic["pattern"].join(['',RomanItem[1][0]])
         if re.search(patstr,RomanStr) != None:
           NumDic["retNum"] += 9*RomanItem[1][4]
           NumDic["pattern"] = patstr
         else:
           patstr = NumDic["pattern"].join(['',RomanItem[1][1]])
           if re.search(patstr,RomanStr) != None:
             NumDic["retNum"] += 4*RomanItem[1][4]
             NumDic["pattern"] = patstr
           else:
             patstr = NumDic["pattern"].join(['',RomanItem[1][2]])
             if re.search(patstr,RomanStr) != None:
               NumDic["retNum"] += 5*RomanItem[1][4]
               NumDic["pattern"] = patstr
       if NumDic["pattern"] == '':
         NumDic["pattern"] = '^'
       tempstr = ''
       sum = 0
       for k in range(0,4):
         pstr = RomanItem[1][3].join(['','{']).join(['',str(k)]).join(['','}'])
         patstr = NumDic["pattern"].join(['',pstr])
         if re.search(patstr,RomanStr) != None:
           sum = k*(10**i)
           tempstr = patstr
       if tempstr <> '':
         NumDic["pattern"] = tempstr
       else:
         NumDic["pattern"] = patstr
       NumDic['retNum'] += sum
       i -= 1
     return NumDic['retNum']
   else:
     print 'String is not a valid Roman numerals'