Romannumerals1

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

def previous_is_combo(numeral, index):
    if index - 1 < 0:
        return False

    current = NUMERALS[numeral[index]] # Current number extracted from the dictionary
    previous = NUMERALS[numeral[index-1]] # Previous number extracted from the dictionary

    if current > previous:
        return True
    else:
        return False


def next_is_combo(numeral, index):
    current = NUMERALS[numeral[index]] # Current number extracted from the dictionary
    try:
        next = NUMERALS[numeral[index+1]] # Next number extracted from the dictionary
    except IndexError:
        return False

    if current < next:
        return True
    else:
        return False

def compare(numeral, index):
    if next_is_combo(numeral, index):
        return NUMERALS[numeral[index+1]] - NUMERALS[numeral[index]]
    elif previous_is_combo(numeral, index):
        return 0
    else:
        return NUMERALS[numeral[index]]

def numeral_to_decimal(numeral):
    decimal = 0

    for letter in range(len(numeral)):
        decimal += compare(numeral, letter)

    return decimal

def main():
    print(numeral_to_decimal("MCMLIV"))
    print()
    print(numeral_to_decimal("MMVIII"))
    print()
    print(numeral_to_decimal("MCMXC"))
    print()
    print(numeral_to_decimal("MCDIV"))

if __name__ == "__main__":
    main()