Changing state of buttons.

Eric Brunel eric_brunel at
Fri Sep 10 09:54:49 CEST 2004

Jamey Saunders wrote:
> Hi all,
> I'm just learning Python (I'm about 8 hours in so far), and I have a
> problem.  I'm writing a small Windows app using Tkinter.  I have two
> buttons on my screen that I want to start in an inactive state
> (already have that working) and when two input fields have some data
> input, the buttons would become active.  What's the best way to go
> about changing the state of buttons that already exist?
> Thanks!

I'm not sure I understand the meaning of your question: if it's really about 
changing the state of an existing widget, a simple 
widget.configure(state=NORMAL) will do what you want.

But the tricky part of what you want to do does not seem to be there: doing an 
action whenever the text of an entry changes is a bit tricky with Tkinter. Here 
is an example:

from Tkinter import *

root = Tk()

## Create the entry and associated variable
v = StringVar()
e = Entry(root, textvariable=v)

## Create the button
b = Button(root, text='OK', command=root.quit, state=DISABLED)

## Function making the button active if needed
def makeBActive(*args):
   ## If there is something in the entry, activate the button
   if v.get().strip():
   ## Otherwise de-activate it

## Whenever a key is released in the entry, call the function above
e.bind('<KeyRelease>', makeBActive)


- Eric Brunel <eric (underscore) brunel (at) despammed (dot) com> -
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