8. String to Integer (atoi)

class Solution(object):
    def myAtoi(self, str):
        """
        :type str: str
        :rtype: int
        """
        
        # get the ord from 0 to 9
        
        strNum =['0','1','2','3','4','5','6','7','8','9']
        as2num = [ ord(x) for x in strNum] 
        sign = 0
        reslist = []
        res = 0
        
        for char in str:
            
            if ord(char) == ord('-') and sign ==0 and len(reslist)==0:
                sign = -1
            elif ord(char) == ord('+') and sign ==0 and len(reslist)==0:
                sign = 1
            elif ord(char) == ord('-') and sign ==0 and len(reslist)!=0:
                break
            elif ord(char) == ord('+') and sign ==0 and len(reslist)!=0:
                break            
            
            elif ord(char) in as2num:
                reslist.append(ord(char)-ord('0'))
            elif ord(char) == ord('-') and sign !=0 :
                break
            elif ord(char) == ord('+') and sign !=0 :
                break
            elif char is not ' ' and char not in as2num and (ord(char)!= ord('-') or ord(char)!= ord('+')):
                break
            elif char is ' ' and len(reslist)>0:
                break
            elif char is ' ' and sign !=0:
                break
        
        for num in reslist:
            res = res*10 + num
        if sign == -1:
            res = 0 - res
        
        if res > 2**31-1:
            return 2**31-1
        if res < -2**31:
            return -2**31
        
        
        return res