old_contents: #!/usr/bin/env python3
  # -*- coding: utf-8 -*-
  
  # Copyright (c) 2016 Jérémie DECOCK (http://www.jdhp.org)
  
  # Permission is hereby granted, free of charge, to any person obtaining a copy
  # of this software and associated documentation files (the "Software"), to deal
  # in the Software without restriction, including without limitation the rights
  # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  # copies of the Software, and to permit persons to whom the Software is
  # furnished to do so, subject to the following conditions:
  
  # The above copyright notice and this permission notice shall be included in
  # all copies or substantial portions of the Software.
   
  # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  # THE SOFTWARE.
  
  # See also: http://effbot.org/tkinterbook/listbox.htm
  
  import tkinter as tk
  
  root = tk.Tk()
  
  # The "selectmode" can be:
  # - SINGLE:   just a single choice
  # - BROWSE:   same, but the selection can be moved using the mouse
  # - MULTIPLE: multiple item can be choosen, by clicking at them one at a
  #             time
  # - EXTENDED: multiple ranges of items can be chosen, using the Shift and
  #             Control keyboard modifiers
  listbox = tk.Listbox(root, selectmode=tk.EXTENDED)
  listbox.pack(side=tk.TOP)
  
  items = ["banana", "apple", "mango", "orange"]
  for item in items:
      listbox.insert(tk.END, item)
  
  def print_selection():
      print(listbox.curselection())
      print([items[item] for item in listbox.curselection()])
  
  button = tk.Button(root, text="Print selection", width=15, command=print_selection)
  button.pack(side=tk.BOTTOM)
  
  root.mainloop()
  
  
new_contents: #!/usr/bin/env python3
  # -*- coding: utf-8 -*-
  
  # Copyright (c) 2016 Jérémie DECOCK (http://www.jdhp.org)
  
  # Permission is hereby granted, free of charge, to any person obtaining a copy
  # of this software and associated documentation files (the "Software"), to deal
  # in the Software without restriction, including without limitation the rights
  # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  # copies of the Software, and to permit persons to whom the Software is
  # furnished to do so, subject to the following conditions:
  
  # The above copyright notice and this permission notice shall be included in
  # all copies or substantial portions of the Software.
   
  # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  # THE SOFTWARE.
  
  # See also: http://effbot.org/tkinterbook/listbox.htm
  
  import tkinter as tk
  
  root = tk.Tk()
  
  # LISTBOX #############################
  
  # The "selectmode" can be:
  # - SINGLE:   just a single choice
  # - BROWSE:   same, but the selection can be moved using the mouse
  # - MULTIPLE: multiple item can be choosen, by clicking at them one at a
  #             time
  # - EXTENDED: multiple ranges of items can be chosen, using the Shift and
  #             Control keyboard modifiers
  listbox = tk.Listbox(root, selectmode=tk.EXTENDED)
  listbox.pack(side=tk.TOP)
  
  items = ["banana", "apple", "mango", "orange"]
  
  for item in items:
      listbox.insert(tk.END, item)
  
  # BUTTON ##############################
  
  def print_selection():
      selection_id_tuple = listbox.curselection()
      selection_label_tuple = tuple(listbox.get(item) for item in selection_id_tuple)
      print(selection_id_tuple)
      print(selection_label_tuple)
  
  button = tk.Button(root, text="Print selection", width=15, command=print_selection)
  button.pack(side=tk.BOTTOM)
  
  # MAIN LOOP ###########################
  
  root.mainloop()
  
  
subject: Improve a snippet.