def ask(question, choices):
    """Prompt user for a choice from a list. Return the choice."""
    choices_lc = [x.lower() for x in choices]
    user_choice = ""
    match = False
    while not match:
        print(question)
        user_choice = input("[" + "/".join(choices) + "] ? ").strip().lower()
        for choice in choices_lc:
            if user_choice.startswith(choice):
                match = True
                break
    return user_choice