Mailing List Archive

Ole-Kristian Villaboe wrote:

> Is there anyway an altering of a variable (Int-, String- or Double-)
> (by the user, via the GUI) could call a function in order to tell the
> environment that it has changed since the initial setting(or a static
> comparison value)
>
> Ole-Kr. Villaboe
>
> Sent via Deja.com http://www.deja.com/
> Share what you know. Learn what you don't.

You could use the lostfocus event of the widget

Pierrette

Ole-Kristian Villaboe <olevi@my-deja.com> wrote:
> Is there anyway an altering of a variable (Int-, String- or Double-)
> (by the user, via the GUI) could call a function in order to tell the
> environment that it has changed since the initial setting(or a static
> comparison value)

Assuming you're talking about Tkinter here: below's an example of using
trace() to trace a variable:

class VLabel(Label):
"""VLabel class - becomes red when textvariable.valid() returns
false"""

def __init__(self, master, textvariable, **cnf):
apply(Label.__init__, (self, master), cnf)
self.config(textvariable=textvariable)
self.textvariable = textvariable
textvariable.trace('w',self.notify)

def notify(self, *args):
if self.textvariable.valid():
self.config(bg=self.config('bg')[3])
else:
self.config(bg='red')

Everytime the textvariable is changed notify() gets called, which checks
whether the textvariable is valid. If not, the background is colored red,
if it is valid, the background is set to its default color.

HTH, Frank
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