title: Changing the options of a OptionMenu when clicking a Button
body: <p>Say I have an option menu <code>network_select</code> that has a list of networks to connect to.</p>
  
  <pre><code>import Tkinter as tk
  
  choices = ('network one', 'network two', 'network three')
  var = tk.StringVar(root)
  network_select = tk.OptionMenu(root, var, *choices)
  </code></pre>
  
  <p>Now, when the user presses the refresh button, I want to update the list of networks that the user can connect to.</p>
  
  <ul>
  <li>I don't I can use <code>.config</code> because I looked through <code>network_select.config()</code> and didn't see an entry that looked like the choices I gave it.</li>
  <li>I don't think this is something one can change using a tk variable, because there is no such thing as a <code>ListVar</code>.</li>
  </ul>