Tkinter - centering, positioning new windows

[Thomas Lane]

Does anyone know how to specify the position of a Toplevel window? I
haven't been able to find any documentation on this. I would especially
like to be able to center a window on the screen and center a window
respective to its parent window. I know this must be possible, since
dialogs popped up by TkMessageBox do this. As usual, any help would be
greatly appreciated.

-Tom