atoi

class Solution:
    def atoi(self, str):
        """
        :type str: str
        :rtype: int
        """
        i = 0
        result = 0
        length_of_number=0
        numberarray=[]
        intMAX=2**31 -1
        intnegMAX=2**31
        negative = False
        while i <= len(str):
            if i == len(str):
                return 0
            if str[i] == '+' or str[i] == '-':
                if str[i] == '-':
                    negative = True
                i += 1
                break
            else:
                if str[i] == ' ':
                    i += 1
                else:
                    break
        while i <= len(str):
            if i == len(str):
                return 0
            if str[i] == '0':
                i += 1
            else:
                break
        while i <= len(str):
            if i == len(str):
                break
            if str[i] in ['0','1', '2', '3', '4', '5', '6', '7', '8', '9']:
                length_of_number += 1
                numberarray.append(int(str[i]))
                i += 1
            else:
                break
        for nu in numberarray:
            result += nu*10**(length_of_number-1)
            length_of_number-=1
        if negative:
            if result <= intnegMAX:
                result*=-1
            else:
                result = intnegMAX
                result*=-1
        else:
            if result > intMAX:
                result = intMAX
        return result