Basic Calculator III

calc.py

class Solution:
    """
    @param s: the expression string
    @return: the answer
    """

    def calculate(self, s):
        i = 0
        left_brac_indexes = []
        while i < len(s):
            char = s[i]
            if char == "(":
                left_brac_indexes.append(i)
                i += 1
            elif char == ")":
                inner_result = str(
                    self.calculate_no_bracket(s[left_brac_indexes[-1] + 1 : i])
                )
                s = s[: left_brac_indexes[-1]] + inner_result + s[i + 1 :]
                i = left_brac_indexes[-1] + len(inner_result)
                left_brac_indexes.pop()
            else:
                i += 1

        return self.calculate_no_bracket(s)

    def calculate_no_bracket(self, s):
        groups = (
            s.replace("--", " + ")
            .replace("+", " + ")
            .replace("-", " - ")
            .replace("*", " * ")
            .replace("/", " / ")
            .replace("-", "+ -1 *")
            .strip()
            .split("+")
        )
        return sum([self.calc(g) for g in groups])

    @staticmethod
    def calc(group: str):
        if not group or group.isspace():  # Could be empty string, e.g. '+ 4'.split('+')
            return 0
        elems = group.strip().split()
        result = int(elems[0])
        for i in range(1, len(elems), 2):
            if elems[i] == "*":
                result *= int(elems[i + 1])
            elif elems[i] == "/":
                result = int(result / int(elems[i + 1]))
        return result