python roman numeral converter

1def roman_to_int(s):
2    rom_val = {'I': 1, 'V': 5, 'X': 10, 'L': 50, 'C': 100, 'D': 500, 'M': 1000}
3    int_val = 0
4    for i in range(len(s)):
5        if i > 0 and rom_val[s[i]] > rom_val[s[i - 1]]:
6            int_val += rom_val[s[i]] - 2 * rom_val[s[i - 1]]
7        else:
8            int_val += rom_val[s[i]]
9    return int_val
10
11def int_to_roman(num):
12    val = [
13            1000, 900, 500, 400,
14            100, 90, 50, 40,
15            10, 9, 5, 4,
16            1
17            ]
18    syb = [
19            "M", "CM", "D", "CD",
20            "C", "XC", "L", "XL",
21            "X", "IX", "V", "IV",
22            "I"
23            ]
24    roman_num = ''
25    i = 0
26    while  num > 0:
27        for _ in range(num // val[i]):
28            roman_num += syb[i]
29            num -= val[i]
30        i += 1
31    return roman_num
32
33print(roman_to_int("IIV"))
34print(int_to_roman(3431))