Convert numbers in Roman numerals to Arabic numerals.

rom2arabic.py

# -*- coding: utf-8 -*-
#!/usr/bin/env python
import sys
import os

m = {
    'I': 1,
    'V': 5,
    'X': 10,
    'L': 50,
    'C': 100,
    'D': 500,
    'M': 1000
}


def roman(r):
    try:
        r = int(r)
    except ValueError:
        r = str(r).replace(' ', '').upper()
        if not set(m) >= set(r):
            raise ValueError('Not a valid Roman numeral: %r' % r)
        values = map(m.get, r)
        value = sum(-n if n < max(values[i:]) else n
                    for i, n in enumerate(values))
        return value
    raise ValueError('Not a valid Roman numeral: %r' % r)


def main():
    for i in sys.stdin:
        sys.stdout.write('%d\n' % roman(i.strip(os.linesep)))

if __name__ == "__main__":
    main()


### We can also use pip install rome==0.0.3
# from rome import Roman
# for i in sys.stdin:
#     sys.stdout.write('%d\n' % int(Roman(i.strip(os.linesep))))