An example of a simple menu loop in Python.

menu_example.py

#!/usr/bin/env python3

COLORS =  {
    "r": "red",
    "o": "orange",
    "y": "yellow",
    "g": "green",
    "b": "blue",
    "i": "indigo",
    "v": "violet",
    "u": "ultraviolet",
}

def show_choices() -> None:
    for key in COLORS.keys():
        print(f"  {key}. {COLORS[key]}")

def choose_color() -> str:
    while True:
        # Display the available color choices.
        show_choices()

        # Prompt the user for a color choice.
        choice = input("Choose a color: ").lower()

        # Validate the user's choice.
        if choice in COLORS.keys():
            return COLORS[choice]
        else:
            print()
            print(f"Invalid choice '{choice}'. Please try again.")

def main() -> None:
    value = choose_color()
    print(f"You chose the color {value}.")

if __name__ == "__main__":
    main()