8. 字符串转换整数 (atoi)

import re
import math
class Solution(object):
    def myAtoi(self, str):
        """
        :type str: str
        :rtype: int
        """        
        r1 = re.match(r‘\s*[\-\+]?\d+‘,str)
        if r1!=None :
            r2=int(r1.group())
            if r2<=-2147483648:
                return -2147483648
            elif r2>=2147483648:
                return 2147483647
            else:
                return r2
        else:
            return 0