def onselect(evt):
# Note here that Tkinter passes an event object to onselect()
w = evt.widget
index = int(w.curselection()[0])
value = w.get(index)
print('You selected item %d: "%s"' % (index, value))
lb = Listbox(frame, name='lb')
lb.bind('<<ListboxSelect>>', onselect)