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/checkbutton.htm
  
  import tkinter as tk
  
  root = tk.Tk()
  
  test_var = tk.IntVar()
  #test_var.set(1)
  
  def callback():
      print("var = ", test_var.get())
  
  checkbutton = tk.Checkbutton(root, text="Test", variable=test_var, command=callback)
  
  # If you need to keep track of both the variable and the widget, you can
  # simplify your code somewhat by attaching the variable to the widget reference
  # object
  #checkbutton.var = test_var
  
  checkbutton.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/checkbutton.htm
  
  import tkinter as tk
  
  root = tk.Tk()
  
  test_var = tk.IntVar()
  #test_var.set(1)
  
  def callback():
      print("var = ", test_var.get())
  
  checkbutton = tk.Checkbutton(root, text="Test", variable=test_var, command=callback)
  
  checkbutton.pack()
  
  root.mainloop()
  
  
subject: Update a snippet.