Python将阿拉伯数字转换为罗马数字的方法

def numToRomanNum(Num): """digital will be converted into Roman numerals,Ex: numToRomanNum(3999)"""   if Num < 1 or Num > 3999:     print 'The Num must in 1-3999'   else:     NumDic = {       '1':('I','IV','V','IX'),       '2':('X','XL','L','XC'),       '3':('C','CD','D','CM'),       '4':('M')       }     items = sorted(NumDic.items())     retstr = ''     for item in items:       str = ''       (Num,modNum) = divmod(Num,10)       if modNum != 0:         if item[0] != '4':           if modNum <= 3:             while modNum > 0:               str = str.join(['',item[1][0]])               modNum -= 1           elif modNum < 5:             str = item[1][1]           elif modNum == 5:             str = item[1][2]           elif modNum < 9:             str = item[1][2]             while modNum > 5:               str = str.join(['',item[1][0]])               modNum -= 1           else:             str = item[1][3]         else:           while modNum > 0:             str = str.join(['',item[1][0]])             modNum -= 1         retstr = str.join(['',retstr])     return retstr