Tkinkter - how can I control where the main widget appears

[DoubleM]

Given the following trivial program:

from Tkinter import *

root = Tk()
l = Label(root, text = "Hi There")
l.pack()
root.mainloop()


How can I control where the main window appears on the screen?  Ideally, I
would like to center it.

Thanks for your help,
Mike