How to prevent Function B returning 'none' to Function A that calls it, after function B calls function C and returns to itself

Question

Apologies for the confusing title, but here is a very simplified version of what I mean:

def main():
    burger = 0
    shake = 0

    run = True
    while run:
        choice = show_menu()

        if choice == "burger":
            qt_burger += 1
        elif choice == "shake":
            qt_shake += 1
        else:
            show_bill

def show_menu():
    choice = input("Burger or Shake?: ")
    if choice not in ["burger", "shake"]:
        show_error(choice)
    else:
        return choice

def show_error(choice):
    print(f"{choice} is not an option")
    show_menu()

main()

Function 'main' defines variable 'choice' based on what is returned from function 'show_menu'. If show_menu does not call show_error, the program properly returns the input value back to 'choice' in 'main'. However, if show_error is called, show_menu is called again, and a proper value is entered the second time, choice in main becomes 'none'. Is there any way around this while keeping all these separate functions? I have also tried re-calling show_menu from within itself rather than from within the error function, but it is the same result.

But if you recurse, you need to return a value when recursing: `return show_error(choice)` and `return show_menu()` — Barmar, Jul 09 '22 at 04:29

Sandeep Rawat · Accepted Answer · 2022-07-09T04:44:32.380

Incase of choice is invalid, you are calling show_error, after executing this function(show_error) the interpreter will just move to next line i.e the end of show_menu function which implicitly return None .But if you return show_error(), the interpreter will execute this function and return whatever value show_error will return.


def show_menu():
    choice = input("Burger or Shake?: ")
    if choice not in ["burger", "shake"]:
        return show_error(choice)
    else:
        return choice

def show_error(choice):
    print(f"{choice} is not an option")
    return show_menu()

A simpler(more readable) way can be

def read_input():
    return input("Burger or Shake?: ")

def show_menu():
    choice = read_input()
    while choice not in ["burger", "shake"]:
        show_error(choice)
        choice = read_input()
    return choice

def show_error(choice):
    print(f"{choice} is not an option")

How to prevent Function B returning 'none' to Function A that calls it, after function B calls function C and returns to itself

1 Answers1