class Solution:
    def myAtoi(self, s: str) -> int:
        flag = 1
        s = s.strip(' ')  
        if len(s) == 0: return 0  

        if s[0] in '-+':
            if s[0] == '-': flag = -1
            s = s[1:]

        if len(s) == 0:
            return 0

        num = ''
        for ch in s:
            if '0' <= ch <= '9':
                num = num + ch
            else:
                break

        if len(num) < 1 or num == 0:
            return 0

        return max(min(int(num) * flag, 2 ** 31 - 1), -2 ** 31)