Leetcode 8. String to Integer (atoi)

class Solution:
    def myAtoi(self, str: str) -> int:
        tmp = ''
        res = 0
        
        for i in range(len(str)):
            if str[i] == ' ': continue
            elif str[i].isalpha() or str[i] == '.': break
            elif str[i].isdigit():
                tmp += str[i]
                if i+1 < len(str) and not str[i+1].isdigit(): break
            elif str[i] == '-' or str[i] == '+':
                if i+1 < len(str) and str[i+1].isdigit(): tmp += str[i]
                else: break
                
        res = int(tmp) if tmp else 0
        if -2**31 <= res <= 2**31-1: return res
        else: return -2**31 if res < 0 else 2**31-1

https://leetcode.com/problems/string-to-integer-atoi/