Validating Entry in tkinter

[Saul Spatz]

Thanks so much, this is great.  I want to validate that the user is entering a string appropriate for bytes.fromhex.  Here's how I modified your validate funtion:

def validate(before, after):
    print(before, "-->", after)
    #return after.isdigit()
    return after[-1] in '1234567890abcdefABCDEF '
    
I also had to change validate="all" to validate="key" in the Entry construction, since otherwise, I go an IndexError when the widget gets the focus.  (try...except also worked, but I only care about keystrokes.)

I didn't know about the register method; that's the key.

Thanks again,
Saul