Number to Roman Numerals & Reverse

values ={'I': 1, 'V': 5, 'X': 10, 'L': 50, 'C': 100, 'D': 500, 'M': 1000}
dvs = sorted(values.items(), key=lambda x:x[1], reverse=True)

def converter(num):
    def roman2int(s):
        num  = 0
        while s:
            n, m = f'{s}0'[:2]
            n, m = values[n], values.get(m, 0)
            num += max(m-n, n)
            s = s[1+(m>n):]
        return num

    def int2roman(num):
        if num < 0: return None
        if num ==0: return ''

        for k, v in dvs:
            for k2, v2 in dvs:
                rem = v - v2
                if (v2 < num < v) and (num >= rem) and (rem != v2):
                    v = rem
                    k = k2 + k
                    break
            if (roman:=int2roman(num-v)) != None:
                return k + roman
        return None

    roman =  int2roman(num)
    number = roman2int(roman)
    print(f'Original: {num} => Roman: {roman} => Number: {number}')


converter(1912)