title: Issue using num pad keys for Python turtle graphics onkey function
body: <p>I am having an issue creating turtle.onkey commands using the numpad 1-9 keys as input.</p>
  
  <p>I looked at the source and documentation, it appears the keys taken as arguments come from tkinker. I found <a href="http://www.tcl.tk/man/tcl8.4/TkCmd/keysyms.htm" rel="nofollow noreferrer">a list</a> of keys from the documentation there as well as <a href="https://infohost.nmt.edu/tcc/help/pubs/tkinter/web/key-names.html" rel="nofollow noreferrer">this list</a> and from what I can gather the argument should be "KP_4" for the number '4' on the numpad, but my code will not take it. I have tried more traditional keys like "Left" for the left arrow and these seem to work fine. I also looked into a document on here about pygame thinking maybe it was similar, but the one they list for the numpad 4 did not work either. (it was K_KP4)</p>
  
  <pre class="lang-py prettyprint-override"><code>def player_move_left():
      x = player_char.xcor()
      x -= player_max_move
      player_char.setx(x)
  turtle.onkey(player_move_left,"K_P4")
  </code></pre>
  
  <p>This should take the x coordinate, and subtract the movement amount then apply that number to the player variable's x-coordinate.</p>
  
  <p><strong>* Solution provided in the first answer*</strong></p>