old_contents: import tkinter as tk
  
  window = tk.Tk()
  window.title('my window')
  window.geometry('200x100')
  
  var = tk.StringVar()
  l = tk.Label(window, textvariable=var, bg='green', font=('Arial', 12), width=15,
               height=2)
  #l = tk.Label(root, text='OMG! this is TK!', bg='green', font=('Arial', 12), width=15, height=2)
  l.pack()
  
  on_hit = False
  def hit_me():
      global on_hit
      if on_hit == False:
          on_hit = True
          var.set('you hit me')
      else:
          on_hit = False
          var.set('')
  
  b = tk.Button(window, text='hit me', width=15,
                height=2, command=hit_me)
  b.pack()
  
  
  window.mainloop()
  
new_contents: # View more python learning tutorial on my Youtube and Youku channel!!!
  
  # Youtube video tutorial: https://www.youtube.com/channel/UCdyjiB5H8Pu7aDTNVXTTpcg
  # Youku video tutorial: http://i.youku.com/pythontutorial
  
  import tkinter as tk
  
  window = tk.Tk()
  window.title('my window')
  window.geometry('200x100')
  
  var = tk.StringVar()
  l = tk.Label(window, textvariable=var, bg='green', font=('Arial', 12), width=15,
               height=2)
  #l = tk.Label(root, text='OMG! this is TK!', bg='green', font=('Arial', 12), width=15, height=2)
  l.pack()
  
  on_hit = False
  def hit_me():
      global on_hit
      if on_hit == False:
          on_hit = True
          var.set('you hit me')
      else:
          on_hit = False
          var.set('')
  
  b = tk.Button(window, text='hit me', width=15,
                height=2, command=hit_me)
  b.pack()
  
  
  window.mainloop()
  
subject: Update tk2_label_button.py