Tkinter question

[Logan]

On Fri, 28 Nov 2003 19:59:23 +0100, Ali El Dada wrote:

> i am using Tkinter in my application, and i have a button
> that, when clicked, opens a new window as in: 
> 
> b1 = Button(someframe, text="bla", command = someFunction)
> 
> def someFunction():
>     newWindow = Toplevel()
>     '''the new window widgets go here'''
> 
> of course, whenever the button is clicked, a new window
> opens. what do you recommend as a neat way to allow only one
> window to open??

It depends on what kind of behavior you want: if newWindow is e.g.
a dialog (like 'find', 'find & replace' etc. in an editor), you
want the new window to pop up, but any older dialog should get 
destroyed. 

To achieve this, you can make newWindow a *global variable* and
use e.g. the following (not very elegant, but it works):

# here, the 'find'-dialog is created (e.g. inside some class)
    try:
	newWindow.destroy()
    except:
        pass

    newWindow = Toplevel()
    # widgets for the 'find'-dialog

# here, the 'find&replace'-dialog is created (e.g. inside some class)
    try:
	newWindow.destroy()
    except:
        pass

    newWindow = Toplevel()
    # widgets for the 'find&replace'-dialog


If you want, that your window gets created only once (and whenever
such a window is already open, no new window should be created) you
could either use an approach similar to the one above (i.e. with
newWindow being a global variable) or e.g. use a class which 
keeps track on how many instances of itself were already created
and which behaves accordingly (Google: python, singleton).

There are other solutions, too. The 'right' solution for you
depends mainly on the design of your whole program (OO or not etc.).

HTH, L.


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