title: Adding items to Listbox in Python Tkinter
body: <p>I would like my Listbox widget to be updated upon clicking of a button. However I encountered a logic error. When I click on the button, nothing happens. No errors at all.</p>
  
  <pre><code>listOfCompanies: [[1, ''], [2, '-'], [3, '@ASK TRAINING PTE. LTD.'], [4, 'AAIS'], [5, 'Ademco'], [6, 'Anacle']
  
  def populatebox():
              listBox.insert("end", listOfCompanies)
  
  btn = Button(self, text="Update list", command = lambda: populatebox())
  btn.pack()
  </code></pre>