title: Python 3 - Getting amount of items in Listbox widget
body: <p>Is there a way to retrieve a value of the amount of items in a Listbox widget? Such as len() is used for a list, but it cannot be used for Listbox as it gives the following error:</p>
  
  <pre><code>if len(listbox)==0:
  TypeError: object of type 'Listbox' has no len()
  </code></pre>