Source code for trial_project.calculator

import numbers
import sys


class CalculatorError(Exception):
    """An exception class for Calculator"""


class Calculator:
    """A terrible calculator."""

    def add(self, a, b):
        self._check_operand(a)
        self._check_operand(b)
        return a + b

    def subtract(self, a, b):
        return a - b

    def multiply(self, a, b):
        return a * b

    def divide(self, a, b):
        try:
            return a / b
        except ZeroDivisionError:
            raise CalculatorError("Can't divide by zero.")

    def _check_operand(self, operand):
        if not isinstance(operand, numbers.Number):
            raise CalculatorError(f"'{operand}'' was not a number")


if __name__ == "__main__":
    print("Let's calculate!")
    calculator = Calculator()
    operations = [
        calculator.add,
        calculator.subtract,
        calculator.multiply,
        calculator.divide,
    ]

    while True:
        for i, operation in enumerate(operations, start=1):
            print(f"[{i}]: {operation.__name__}")
        print("q: quit")
        operation = input("Pick an operation: ")
        if operation == "q":
            sys.exit()
        op = int(operation)
        a = float(input("What is a? "))
        b = float(input("What is b? "))
        try:
            result = operations[op - 1](a, b)
            print(f"Result is: {result}")
        except CalculatorError as ex:
            print(ex)
        except IndexError as ex:
            print(f"WARNING: choosen operation is not in the list above. \n{ex}")