Tkinter checkbutton switch on and off together

[zazahohonini]

BPO	38898
Nosy	@serhiy-storchaka
Superseder	bpo-29402: Problem with Checkbutton and duplicate last name components
Files	tkinter-checkbutton-bug.ogv: Video demonstatring the problem

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2019-11-28.07:04:43.816>
created_at = <Date 2019-11-22.21:16:20.107>
labels = ['3.8', '3.7', 'expert-tkinter']
title = 'Tkinter checkbutton switch on and off together'
updated_at = <Date 2019-11-28.07:04:43.815>
user = 'https://bugs.python.org/zazahohonini'

bugs.python.org fields:

activity = <Date 2019-11-28.07:04:43.815>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = True
closed_date = <Date 2019-11-28.07:04:43.816>
closer = 'serhiy.storchaka'
components = ['Tkinter']
creation = <Date 2019-11-22.21:16:20.107>
creator = 'zaza hohonini'
dependencies = []
files = ['48741']
hgrepos = []
issue_num = 38898
keywords = []
message_count = 2.0
messages = ['357323', '357375']
nosy_count = 3.0
nosy_names = ['gpolo', 'serhiy.storchaka', 'zaza hohonini']
pr_nums = []
priority = 'normal'
resolution = 'duplicate'
stage = 'resolved'
status = 'closed'
superseder = '29402'
type = None
url = 'https://bugs.python.org/issue38898'
versions = ['Python 3.6', 'Python 3.7', 'Python 3.8']

[zazahohonini]

Hello,

I am running python 3.8.0 and found a problem where multiple checkbuttons get switched when I click one. From observing it looks like each first check button in a frame is linked. And each second, etc. I ran the some program in python 2.7.17 and it works as expected.

Basic program that show the problem:

import tkinter as tk

class Hello(tk.Frame):                     
    def __init__(self, parent=None):
        tk.Frame.__init__(self, parent)
        check = tk.Checkbutton(self, text='Checkbutton')
        check.pack()

root = tk.Tk()
Hello(root).pack()
Hello(root).pack()
root.mainloop()

[zazahohonini]

Hello,

I have done a bit of digging and found out that this behavior appeared in python version 3.6.0 alpha2. I think it is related to bpo-27025
(https://bugs.python.org/issue27025) that changed the way that widgets are named. It is my impression that the code that determines which checkbutton should have its appearance changed has not been changed accordingly.

I also observe that if I use variable=tk.IntVar() as additional argument to tk.Checkbutton, normal behavior is restored. This is the easiest work around.

[questaware]

I am running python 3.10 Tk/Tcl 3.6.10.

It seems that the problem is more widespread.

Adding variable=tk.IntVar() does fix the above problem but there is also this problem:

cb3.txt

[questaware]

Is seems that Checkbutton(frame, variable=myVar) does not cause Checkbutton to retain a python reference to myVar so that it can be garbage collected. Presumably this bug/behaviour occurs because the implementation is in "C"? Of course the system must retain a reference to myVar in some form so that it can update myVar when the button is clicked!

[serhiy-storchaka]

This issue was closed as a duplicate of #73588.