atoi leetcode
class Solution(object):
def myAtoi(self, s):
"""
:type str: str
:rtype: int
"""
###better to do strip before sanity check (although 8ms slower):
#ls = list(s.strip())
#if len(ls) == 0 : return 0
if len(s) == 0 : return 0
ls = list(s.strip())
sign = -1 if ls[0] == '-' else 1
if ls[0] in ['-','+'] : del ls[0]
ret, i = 0, 0
while i < len(ls) and ls[i].isdigit() :
ret = ret*10 + ord(ls[i]) - ord('0')
i += 1
return max(-2**31, min(sign * ret,2**31-1))