def string_checker(question, valid_ans=["yes", "no"]):
    """Checks users enter a valid answer based on a list.
    Accepts first letter or full word"""

    error = f"Please enter a valid response.  Choose {valid_ans}"

    while True:
        # Get user response and make sure it's lowercase
        user_response = input(question).lower()

        for item in valid_ans:
            # check if the user response is a word in the list
            if item == user_response:
                return item

            # check if the user response is the same as
            # the first letter of an item in the list
            elif user_response == item[0]:
                return item

        # print error if user does not enter something that is valid
        print(error)
        print()


# Main Routine

# Valid answers for string checker

rps_valid_ans = ("rock", "paper", "scissors", "xxx")

want_instructions = string_checker("Do you want to see the instructions?")

user_choice = string_checker("Choose:", rps_valid_ans)
print("You chose: ", user_choice)