roman number to integer

roman_to_int.py

def roman_to_int(src):
    convert_map = {
        'I' : 1,
        'V' : 5,
        'X' : 10,
        'L' : 50,
        'C' : 100,
        'D' : 500,
        'M' : 1000
    }
    prev, lst = 0, []
    for x in src.upper()[::-1]:
        i = convert_map[x]
        if i < prev:
            lst.append(-1 * i)
        else:
            lst.append(i)
        prev = i
    return sum(lst)