title: Python Tkinter multiple selection Listbox
body: <p>I have a listbox which is setup with <code>selection='multiple'</code>.
  I then try to obtain a list of all the options the user has selected, by the code <code>name.get(ACTIVE)</code>.
  the problem is that it doesn't not always get all the options I have highlighted in the listbox GUI.</p>
  <p>If I highlight one, it brings this back correctly.<br />
  If I highlight two or more (by a single click on each) it only returns the last item I selected<br />
  If I have multiple highlighted, but then click to un-highlight one, it's this last one I clicked that gets returned even though it unhighlighted.</p>
  <p>I'm expecting for the code to bring back what ever is highlighted.</p>
  <p>The code to setup the listbox is:</p>
  <pre><code>self.rightBT3 = Listbox(Frame1,selectmode='multiple',exportselection=0)
  </code></pre>
  <p>The code to retreive the selections is:</p>
  <pre><code>selection = self.rightBT3.get(ACTIVE)
  </code></pre>
  <p>This is a screenshot of what the Application looks like in action, at the top you can see the console only registered the one selection (last one I clicked).</p>
  <p><img src="https://i.stack.imgur.com/dZUgt.png" alt="enter image description here" /></p>