Tkinter: passing raw binary data back and forth

[Kevin Russell]

I'm helping Kare Sjolander write a Python interface for Snack,
his Tcl extension for handling sound.  (Prepare to be amazed
when it's done :-).)

One thing I can't figure out is how to pass raw binary data
back and forth between Tcl and Python using Tkinter.  Snack
has a couple of commands which will take binary data out of
a sound object and put it into a Tcl variable and vice versa.
I'd like Python to be able to get at this binary data (just
in case there are any psychotic users out there who want to do
something like write their own wavelet analysis routines in
NumPy).  Using a StringVar doesn't work.

Are there any gurus out there who are intimately familiar
with the guts of Tkinter, or maybe PIL gurus who've solved
similar problems with visual data?

-- Kevin Russell