title: Component not appearing in Tkinter Python interface
body: <p>I just start developping in Python to do some interface with Tkinter.
  There is so many way to do an interface, so I would like to know if the structure of my code is correct.
  Also, I can run my script without error. But, it didn't show me the label ,Hello, world".</p>
  
  <p>Can you explain me what is wrong ?</p>
  
  <pre><code>#!/usr/bin/env python
  # -*- coding: utf-8 -*-
  
  # import 
  import tkinter
  from tkinter import *
  from tkinter.filedialog import *
  from tkinter.messagebox import showerror
  
  class MyFrame(Frame):
      def __init__(self):
          # Definition of the main window
          Frame.__init__(self)
          self.master.geometry("800x800")
          self.master.title("Test application")
  
  
      label = Label(self, text="Hello, world")
      label.pack()
  
  def quit(self):
      sys.exit()
  
  
  # ACTION
  def load_file(self) :
      filename=askopenfilename(filetypes=(("Input files", "*.igs")))
      if filename :
          try:
              print("""here it comes: self.settings["template"].set(filename)""")
          except:                     # &lt;- naked except is a bad idea
              showerror("Open Source File", "Failed to read file\n'%s'" % fname)
          return
  
  
  if __name__=="__main__":
      MyFrame().mainloop()
  </code></pre>