"""
Write a Python program that can simulate a simple calculator, using the console as the exclusive input and output
device. That is, each input to the calculator, be it a number, like 12.34 or 1034, or an operator, like + or =, can be
done on a separate line. After each such input, you should output to the Python console what would be displayed on your
calculator.
"""


# define a function that parses the operators tuple into actual operators and calculates result of the expression
def calc(value1, operator, value2):
    if operator == "+":
        result = value1 + value2
    elif operator == "-":
        result = value1 - value2
    elif operator == "*":
        result = value1 * value2
    elif operator == "/":
        # handles a ZeroDivisionError with an error message
        try:
            result = value1 / value2
        except ZeroDivisionError:
            print("You can't divide by zero, enter a new divisor")
            # exits the function cleanly so result never holds None, preventing errors
            return None
    return result


# define global tuple of potential operators
operators = ("+", "-", "*", "/")


def calculate():
    value1 = None
    operator = None
    value2 = None
    # prompts for user input, exits program if 'q' is entered
    while True:
        user_input = input(
            "Enter a number, mathematic operator (+, -, *, /) or 'q' to quit: "
        )
        if user_input == "q":
            break
        # if user inputs '=', prints message if nothing to calculate, prints 'value1' if stored
        elif user_input == "=":
            if value1 is None:
                print("Nothing to calculate")
            elif value2 is None:
                print(value1)
            # otherwise calls 'calc' function to solve the expression
            else:
                result = calc(value1, operator, value2)
                # if ZeroDivisionError is caught in 'calc' resets 'value2' to None
                if result is None:
                    value2 = None
                # if expression is successfully solved, stores the answer in 'value1' for future use and prints it
                else:
                    value1 = result
                    operator = None
                    value2 = None
                    print(value1)
        # if user input is an operator and 'value2' is not set, stores the operator and prints current state of expression
        elif user_input in operators:
            if value2 is None:
                operator = user_input
                print(value1, operator)
            # if 'value2' is set, calculates the value of stored expression
            else:
                result = calc(value1, operator, value2)
                # if ZeroDivisionError is caught in 'calc' resets 'value2' to None
                if result is None:
                    value2 = None
                # otherwise sets answer of stored expression to 'value1' and 'operator' to the new operator entered, sets 'value2' to None
                else:
                    value1 = result
                    value2 = None
                    operator = user_input
                    print(value1, operator)
        else:
            # if no operator is stored, tries input for valid float value
            if operator is None:
                try:
                    user_input = float(user_input)
                # handle ValueError and print error message
                except ValueError:
                    print("Please enter a valid number or operator")
                    continue
                # Stores input as 'value1' and prints it
                value1 = user_input
                print(value1)
            # if operator is stored, tries input for valid float value
            else:
                try:
                    user_input = float(user_input)
                # handle ValueError and print error message
                except ValueError:
                    print("Please enter a valid number or operator")
                    continue
                # stores input as 'value2' and prints current state of expression
                value2 = user_input
                print(value1, operator, value2)


calculate()