roman_numerals

roman.py

def main():
    while True:
        n = input()
        if 0 < n < 10000:
            break
        print 'Error: input 1 ~ 9999'
    s = str(n)
    c = ''
    try:

        if s[-1] == '4':
            c += 'IV'
        elif s[-1] == '9':
            c += 'IX'
        else:
            if int(s[-1]) >= 5:
                c += 'V' + ((int(s[-1]) - 5) * 'I')
            else:
                c += int(s[-1]) * 'I'

        if s[-2] == '4':
            c = 'XL' + c
        elif s[-2] == '9':
            c = 'XC' + c
        else:
            if int(s[-2]) >= 5:
                c = 'L' + ((int(s[-2]) - 5) * 'X') + c
            else:
                c = int(s[-2]) * 'X' + c

        if s[-3] == '4':
            c = 'CD' + c
        elif s[-3] == '9':
            c = 'CM' + c
        else:
            if int(s[-3]) >= 5:
                c = 'D' + ((int(s[-3]) - 5) * 'C') + c
            else:
                c = int(s[-3]) * 'C' + c

        c = int(s[-4]) * 'M' + c

    except IndexError:
        pass

    print c

if __name__ == '__main__':
    main()