title: Update label content on click using Python
body: <p>I'm trying to update the content of a label, in Python, by clicking a button. For each clicks a counter will be raised and the value of the label will be updated by the current value of the counter (j). Here is the code:</p>
  
  <pre><code>import time 
  import random
  import MySQLdb
  from Tkinter import *
  j=0
  
  def PrintNumber():
      global j
      j+=1
      print j
      return      
  
  mgui=Tk()
  mgui.geometry('200x200')
  mgui.title('Queue System')
  
  st = Button(mgui, text="Next Customer", command = PrintNumber)
  st.pack()
  f = PrintNumber()
  label = Label(mgui, text=f)
  label.pack()
  
  mgui.mainloop()
  </code></pre>
  
  <p>Please be kind, i'm new in Python. :)</p>