New submission from Javier Dehesa:
When you build a Tkinter interface with variables, if tkinter.Tk.mainloop is
called from a different function that the one creating the variable objects,
then in some cases the widgets associated with the variables will not be set to
the right value. I have not been able to find a consistent pattern, but I have
some examples.
The following script works correctly:
```
import tkinter as tk
from tkinter import ttk
def make_var_cb(root):
v = tk.BooleanVar(root, True)
cb = ttk.Checkbutton(root, text='Checkbutton', variable=v)
cb.pack()
root.mainloop()
if __name__ == '__main__':
root = tk.Tk()
make_var_cb(root)
```
But the following does not (the result is shown in the attached image):
```
import tkinter as tk
from tkinter import ttk
def make_var_cb(root):
v = tk.BooleanVar(root, True)
cb = ttk.Checkbutton(root, text='Checkbutton', variable=v)
cb.pack()
if __name__ == '__main__':
root = tk.Tk()
make_var_cb(root)
root.mainloop()
```
However, the following _does_ work again:
```
def make_var(root):
return tk.BooleanVar(root, True)
def make_cb(root, v):
return ttk.Checkbutton(root, text='Checkbutton', variable=v)
if __name__ == '__main__':
root = tk.Tk()
v = make_var(root)
cb = make_cb(root, v)
cb.pack()
root.mainloop()
```
----------
components: Tkinter, Windows
files: checkbutton_bad.png
messages: 296100
nosy: Javier Dehesa, paul.moore, steve.dower, tim.golden, zach.ware
priority: normal
severity: normal
status: open
title: Widget variable binding does not work if mainloop is called from a
different function
type: behavior
versions: Python 3.5
Added file: http://bugs.python.org/file46954/checkbutton_bad.png
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue30678>
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