selection = " "
while selection not in ("a", "A", "r",  "R", "m", "M", "q", "Q"):
    print("Menu options")
    print("(a)dd a new player to the game")
    print("(r)emove a player from the game")
    print("(m)odify player")
    print("(q)uit game")
    selection = input("Enter your selection: ")
    if selection not in ("a", "A", "r",  "R", "m", "M", "q", "Q"):
        print("Please enter one of 'a', 'r', 'm' or 'q' ")