Reverse Integer

class Solution:
    # @return an integer
    def reverse(self, x):
        if not x:
            return x
        s = str(x)
        first = s[0]
        result = 0
        if (first.isdigit()):
            sub = int(s[::-1])
            if sub < 2147483648:
                result = sub
        else:
            sub = int(s[1:][::-1])
            if sub < 2147483648:
                result = int(first + s[1:][::-1])
        return result