參考:https://steam.oxxostudio.tw/category/python/example/roman.html

 def roman_to_num(a):

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

    str2 = [i for i in a]

    sum1 = 0

    for i in range(len(str2)):

        str2[i] = int(table[str2[i]])

    str2.reverse()

    sum1 = str2[0]

    for i in range(1, len(str2)):           

      if str2[i] < str2[i-1]:   

        sum1 = sum1 - str2[i]    

      else:

        sum1 = sum1 + str2[i]  

    return sum1

比較麻煩應該是這段