Calculator

from collections import deque
import re


class MathExpressionException(ValueError):
    pass


def calculator_math_express(expr: str) -> float:
    work_stack = deque()
    work_list = []
    i = 0
    temp_expr = expr
    try:
        while len(temp_expr) > 0:
            work_element = re.match(r'(\d+(\.\d+)?)|\(|\)|\*|\+|-|/', temp_expr).group(0)
            temp_expr = temp_expr[len(work_element):]
            if re.match(r'\d+(\.\d+)?', work_element) != None:
                work_list.append(float(work_element))
                if len(work_stack) != 0:
                    if work_stack[len(work_stack) - 1] == '*' or work_stack[len(work_stack) - 1] == '/':
                        work_list.append(work_stack.pop())
            elif work_element == '+' or work_element == '-' or work_element == '(' or work_element == '*' or work_element == '/':
                if work_element == '+' or work_element == '-':
                    if len(work_stack) != 0:
                        if work_stack[len(work_stack) - 1] == '-' or work_stack[len(work_stack) - 1] == '+':
                            work_list.append(work_stack.pop())
                work_stack.append(work_element)
            elif work_element == ')':
                while work_stack[len(work_stack) - 1] != '(':
                    work_list.append(work_stack.pop())
                work_stack.pop()
                if len(work_stack) != 0:
                    if work_stack[len(work_stack) - 1] == '*' or work_stack[len(work_stack) - 1] == '/':
                        work_list.append(work_stack.pop())
            if len(temp_expr) == 0:
                while len(work_stack) > 0:
                    work_list.append(work_stack.pop())
        temp = ''
        while len(work_list) > 1:
            for i in range(len(work_list)):
                if work_list[i] in ['*', '/', '+', '-']:
                    if work_list[i] == '*':
                        temp = work_list[i - 2] * work_list[i - 1]
                    elif work_list[i] == '/':
                        temp = work_list[i - 2] / work_list[i - 1]
                    elif work_list[i] == '+':
                        temp = work_list[i - 2] + work_list[i - 1]
                    elif work_list[i] == '-':
                        temp = work_list[i - 2] - work_list[i - 1]
                    if len(work_list) > 3:
                        temp_list = work_list[i+1:]
                        work_list = work_list[:i - 2]
                        work_list.append(temp)
                        work_list += temp_list
                    else:
                        work_list = [temp]
                    break
        return float(work_list[0])
    except:
        raise MathExpressionException(expr)