BulkCalculator

import re
from _collections import deque

# BULK CALCULATOR APP
# Calculates a single line of values given as a single string e.g. "£10 + £10 - £10 * 0.5"

class Calculator:
    def __init__(self, data: str):
        self.data = data

    @staticmethod
    def add(value1, value2):
        result = value1 + value2
        return result

    @staticmethod
    def subtract(value1, value2):
        result = value1 - value2
        return result

    @staticmethod
    def multiply(value1, value2):
        result = value1 * value2
        return result

    @staticmethod
    def divide(value1, value2):
        try:
            result = value1 / value2
        except ZeroDivisionError:
            return 'Cannot divide to 0.'
        return result

    def analysing_data(self):
        data = deque()
        pattern = r"((-?(?:\d+(?:\.\d+)?))|([-+\/*()])|(-?\.\d+))"
        result = re.finditer(pattern, self.data)

        for element in result:
            data.append(element.group())

        return data

    def calculating(self):
        data = self.analysing_data()
        result = float(data.popleft())

        while data:
            current_operator = data.popleft()
            value = float(data.popleft())

            operations_map = {
                '+': self.add(result, value),
                '-': self.subtract(result, value),
                '*': self.multiply(result, value),
                '/': self.divide(result, value),
            }

            result = operations_map[current_operator]

        return f"{result:.2f}"


app = Calculator('20 + 100 - 10 - 100')
print(app.calculating())