How to check the output of an inner function in the outer function without an unbound local error?

Question

I'm working on my first calculator in python, and I need a method of storing the input of the inner function so that when I run the outer function again, it will check the result to see if it's already been run.

power_on = True

def calculator():
    num_1 = float(input("What is the first number?\n"))
    operation = input("What is the operation?\n")
    num_2 = float(input("What is the second number?\n"))
    if result != None:
        num_1 = int(result)
        operation = input("What is the operation? \n +, -, *, / \n")
        num_2 = float(input("What is the second number?"))
    def calculate():
        if operation == "+":
            return num_1 + num_2
        elif operation == "-":
            return num_1 - num_2
        elif operation == "*":
            return num_1 * num_2
        elif operation == "/":
            return num_1 / num_2
        else:
            return "Invalid operation"
    result = calculate()
    print(f"{num_1} {operation} {num_2} = {result}")
    usercont = input(f"Would you like to continue operating with {result}? \nEnter Y to continue, enter N to restart\n")
    if usercont == "N":
        result = None

while power_on == True:
    calculator()

As you can see, this will generate an unbound local error because we're checking whether result has a value or not before we get a value from the inner function. The issue is that I have no way to correct this error without overwriting whatever the result actually is... if I assign result = "" under def calculator() then I solve the error but never retain my value.

I know this is a noob question but I would appreciate any help for figuring this out.

Thank you.

Answer 1

If you declare the result variable outside of a loop and initialize it to None, you can reference that when choosing to ask about num_1 or not.

like this:

power_on = True

def calculate(operation, num_1, num_2):
    if operation == "+":
        return num_1 + num_2
    elif operation == "-":
        return num_1 - num_2
    elif operation == "*":
        return num_1 * num_2
    elif operation == "/":
        return num_1 / num_2
    else:
        return "Invalid operation, dicklicker"

def calculator(power_on):
    result = None  # starts off with no result
    while power_on:
        if result is None: 
            num_1 = float(input("What is the first number?\n"))
        else:
            num_1 = int(result)

            
        operation = input("What is the operation?\n")
        num_2 = float(input("What is the second number?\n"))
        result = calculate(operation, num_1, num_2)
        print(f"{num_1} {operation} {num_2} = {result}")
        usercont = input(f"Would you like to continue operating with {result}?"
                         " \nEnter Y to continue, enter N to restart\n")
        if usercont == "N":
            result = None

calculator(power_on)

I cleaned up a little bit to make it more readable also.