Note : You can use int() built-in function instread of this.
        :type s: str
        :type base: int
        :rtype: int

def base_to_int(s, base):
    """
        Note : You can use int() built-in function instread of this.
        :type s: str
        :type base: int
        :rtype: int
    """
    
    digit = {}
    for i,c in enumerate(string.digits + string.ascii_uppercase):
        digit[c] = i
    multiplier = 1
    res = 0
    for c in s[::-1]:
        res += digit[c] * multiplier
        multiplier *= base
    return res