Python-сообщество

>>> a = "MCMLXXXVIII"
>>> stek = [ ds[x] for x in a ]
>>> reduce(lambda x, y: x - y if x > y else x + y, stek[::-1])
1966 # Не правильно
>>> stek
[1000, 100, 1000, 50, 10, 10, 10, 5, 1, 1, 1] 
>>> stek = [1000, 100, 1000, 50, 30, 5, 3]
>>> reduce(lambda x, y: x - y if x > y else x + y, stek[::-1])
1988 # Правильно

CONV_TABLE = ((1000, 'M'), (900, 'CM'), (500, 'D'), (400, 'CD'),
              (100, 'C'), (90, 'XC'), (50, 'L'), (40, 'XL'),
              (10, 'X'), (9, 'IX'), (5, 'V'), (4, 'IV'), (1, 'I'))
def roman_to_arab(txt):
    txt = txt.upper()
    ret = 0
    for arab, roman in CONV_TABLE:
        while txt.startswith(roman):
            ret += arab
            txt = txt[len(roman):]
    return ret
a = 'MCMLXXXVIII'
print(roman_to_arab(a))

>>> roman_to_arab("VM")
5 # Должно быть 995

num = {
	'I': 1, 
	'V': 5, 
	'X': 10, 
	'L': 50, 
	'C': 100, 
	'D': 500, 
	'M': 1000}
total = 0
a = input()
a.upper()
for i in a:
	for j in range(a.index(i)+1, len(a)):
		if num.get(i) < num.get(a[j]):
			total -= num.get(i)
			break
	else:
		total += num.get(i)
print(total)