ScrolledText (over Tkinter.Text) validation

[Phlip]

Hypo Nt:

I require a multi-line Text field with validation. It should, at 
least, bounce graphic characters outside a small range. After much
messing with the options I have settled on this unhappy medium:

from Tkinter import *

def valid(vent):
    if vent.keysym_num > 255:  return
    
    if vent.char not in "PERU":
        text = vent.widget
        text.event_generate('<Key-BackSpace>')
         
    return
    
aText = Text() 
aText.bind('<KeyRelease>', valid)

aText.pack()
mainloop()

Efforts to be more exact left the cursor in the wrong location, 
or prevented copy-n-paste, or didn't work.

The problem with that code is it fails the chimp-test. If you bang 
the keyboard you can insert characters faster than that recursive

I have liked to have intercepted the KeyPress event and removed 
the character before it went in, but the 'event' object was one-way.

Does anyone have a better method?

-- 
  Phlip