Tkinter File Dialog Question

[Steve Zatz]

In the Tkinter FileSaveAs Dialog - is there any way to get at the
user's selection of a file extension?  If the user creates a file
without an extension, I want to append the "Save as type" extension
(what it's called under Windows), but I don't see any way to get at
the dialog box's value for the file extension.  Any help would be
appreciated.