leetcode String to Integer (atoi) python

class Solution(object):
def myAtoi(self, str):
"""
:type str: str
:rtype: int
"""
intMax=2147483647
intMin=-2147483648
str=str.strip()
strLen = len(str)
if strLen <= 0:
return 0

bolNegative = False
tmp = str[0]
start=0

if tmp == '-' or tmp == '+':
start=1

if tmp == '-':
bolNegative = True
rs=0
for i in range(start, strLen ):
tmp = str[i]
if tmp >= '0' and tmp <= '9':
rs=rs*10+int(tmp)
elif tmp == '-' or tmp == '+':
return 0
else:
break
intTmp = rs
if bolNegative:
intTmp*=-1
if intTmp > intMax:
return intMax
if intTmp < intMin:
return intMin
return intTmp