title: Pressing tab with tkinter Listboxes moves the "Active" underscore but not the cursor
body: <pre><code>l1=Listbox()
  l1.pack(side=LEFT)
  l1.insert(END, *xrange(1,4))
  
  l2=Listbox()
  l2.pack(side=RIGHT)
  l2.insert(END, *'abc')
  </code></pre>
  
  <p>When I press tab, the underscore jumps to the other Listbox, but the cursor only joins in when I start using the up/down arrows. Is it possible to make it hop along together with the underscore, on pressing tab?</p>
  
  <p><strong>Edit</strong>: This is done by binding the Tab key to invoke the select_set() method on the active item:</p>
  
  <pre><code>l1.bind('&lt;Tab&gt;', lambda e: l2.select_set(l2.index(ACTIVE)))
  l2.bind('&lt;Tab&gt;', lambda e: l1.select_set(l1.index(ACTIVE)))
  </code></pre>
  
  <ul>
  <li><p>l.index(ACTIVE) returns the index of the active item, which is the one with the underscore after Tab is pressed. </p></li>
  <li><p>It is then set to be "selected" using l.select_set(), which moves the cursor to it as well.</p></li>
  <li><p>the "e" after lambda is required since any function called from a tkinter bind is implicitly given an event object, though it isn't used in any way here.</p></li>
  </ul>
  
  <p>Hope this comes handy.</p>