On Wednesday, February 1, 2017 at 11:55:35 AM UTC, Terry Reedy wrote:
> On 2/1/2017 1:37 AM, Christian Gollwitzer wrote:
> > Am 01.02.17 um 00:02 schrieb MRAB:
> >> On 2017-01-31 22:34, Christian Gollwitzer wrote:
> >>>> .!frame.!checkbutton
> >>>> .!frame.!checkbutton2
> >>>> .!frame2.!checkbutton
> >>>> .!frame2.!checkbutton2
> >>>
> >>>
> >> Perhaps someone who knows Tcl and tk can tell me, but I notice that in
> >> the first example, the second part of the widget names are unique,
> >> whereas in the second example, the second part of the widget names are
> >> the reused (both "!checkbutton" and "!checkbutton2" occur twice).
> >
> > It is indeed the reason, but it has some strange legacy cause: the
> > default name for the checkbutton-linked variable is the name of the
> > button inside the parent. Therefore creating a checkbutton has the side
> > effect of creating a variable with the button's name.
> >
> > In this case, the first buttons in the frames are linked to a variable
> > called "!checkbutton" and the other two are linked to "!checkbutton2".
> > (a variable name in Tcl can be anything apart from the empty string).
> > This can also be demonstrated by this Tcl script:
> >
> > package require Tk
> >
> > pack [frame .f1]
> > pack [frame .f2]
> >
> > pack [checkbutton .f1.c1 -text "A" ]
> > pack [checkbutton .f1.c2 -text "B" ]
> >
> > pack [checkbutton .f2.c1 -text "C" ]
> > pack [checkbutton .f2.c2 -text "D" ]
> >
> > which is equivalent to the Python code above.
> >
> > Note that this surprising behaviour was corrected for the (modern) ttk
> > widgets, so if "checkbutton" is replaced by "ttk::checkbutton", they are
> > not any longer linked. In Python, that would be
> >
> > from tkinter import ttk
> > ...
> > w = ttk.Checkbutton()
> >
> > (Personally, I'm not using the legacy widgets any longer)
> Christian, could you repeat any relevant parts of your comments on the
> tracker, especially any ideas on how we might fix tkinter?
> https://bugs.python.org/issue29402
> >> Do the names need to be:
> >>
> >> .!frame.!checkbutton
> >> .!frame.!checkbutton2
> >> .!frame2.!checkbutton3
> >> .!frame2.!checkbutton4
> Serhiy considered that but, not knowing that this would cause a
> regression, we both liked numbering within parent better.
>
> There is a similar issue with radiobuttons on ttk.OptionMenus that
> existed *before* the 3.6 name changes.
> https://bugs.python.org/issue25684
> So there seems to be a systematic issue with tk or how we are (mis)using it.
> > Good question. Maybe there should be unique variable names? I.e., if the
> > script is changed into package require Tk
> >
> > pack [frame .f1]
> > pack [frame .f2]
> >
> > pack [checkbutton .f1.c1 -text "A" -variable v1]
> > pack [checkbutton .f1.c2 -text "B" -variable v2]
> >
> > pack [checkbutton .f2.c1 -text "C" -variable v3]
> > pack [checkbutton .f2.c2 -text "D" -variable v4]
> >
> > then they are also not linked.
> --
> Terry Jan Reedy

It looks as if the issue is indeed that the expression to the right of CheckButton(... variable= must be an expression.

This works for me
global checkbix, checkbuttons
checkbix += 1
b = tk.Checkbutton(frame, text=text, variable=checkbuttons[checkbix], ...)