string-to-integer-atoi.py

class Solution(object):
    def myAtoi(self, s):
        """
        :type str: str
        :rtype: int
        """
        s = s.strip()
        sign = 1
        if not s:
            return 0
        if s[0] in ["+", "-"]:
            if s[0] == "-":
                sign = -1
            s = s[1:]
        ans = 0
        for c in s:
            if c.isdigit():
                ans = ans * 10 + int(c)
            else:
                break
        ans *= sign
        if ans > 2147483647:
            return 2147483647
        if ans < -2147483648:
            return -2147483648
        return ans