title: How to center a Tkinter widget?
body: <p>I have Tkinter window with <code>canvas</code> and <code>label</code> with 200x200 picture on it.
  I want <code>label</code> to be in the center of the window, regardless of the window size.</p>
  
  <pre><code>from Tkinter import *
  import Image, ImageTk, ImageDraw
  
  imgsize = (200,200)
  canvas_bg = "#000000"
  
  root = Tk()
  ## root.geometry("350x350")
  
  panel = PanedWindow()
  panel.pack(expand=0)
  
  canvas = Canvas(panel, bg=canvas_bg)
  
  blank_source = Image.new('RGBA',imgsize, "#ffffff")
  blank = ImageTk.PhotoImage(blank_source)
  
  label = Label(canvas, image=blank)
  label.configure(image = blank)
  
  canvas.pack( expand=0)
  mainloop()
  </code></pre>
  
  <p>Is there any way to do it?</p>