title: Python Tkinter GUI, navigate menus using keyboard only
body: <p>I am trying to build a simple menu using Tkinter. It has 4 buttons, three of which open a new menu. I'd like the menu to be navigated using only the keyboard (i.e the directional buttons and return key). Using both mouse and keyboard would also be acceptable (i.e being able to use either mouse or keyboard to navigate). </p>
  
  <p>How would I go about doing this? </p>