Tkinter mainloop raises when setting the value of ttk.LabeledScale

[goyodiaz]

BPO	27939
Nosy	@serhiy-storchaka
PRs	[Do Not Merge] Convert Misc/NEWS so that it is managed by towncrier #552
Files	tkinter_intvar_float_value.patch

^{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 = 'https://github.com/serhiy-storchaka'
closed_at = <Date 2016-10-30.16:53:56.916>
created_at = <Date 2016-09-02.10:20:34.545>
labels = ['3.7', 'type-bug', 'expert-tkinter']
title = 'Tkinter mainloop raises when setting the value of ttk.LabeledScale'
updated_at = <Date 2017-03-31.16:36:26.919>
user = 'https://bugs.python.org/goyodiaz'

bugs.python.org fields:

activity = <Date 2017-03-31.16:36:26.919>
actor = 'dstufft'
assignee = 'serhiy.storchaka'
closed = True
closed_date = <Date 2016-10-30.16:53:56.916>
closer = 'serhiy.storchaka'
components = ['Tkinter']
creation = <Date 2016-09-02.10:20:34.545>
creator = 'goyodiaz'
dependencies = []
files = ['45203']
hgrepos = []
issue_num = 27939
keywords = ['patch']
message_count = 3.0
messages = ['274223', '279307', '279732']
nosy_count = 3.0
nosy_names = ['python-dev', 'serhiy.storchaka', 'goyodiaz']
pr_nums = ['552']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue27939'
versions = ['Python 3.5', 'Python 3.6', 'Python 3.7']

[goyodiaz]

Calling mainloop after setting the value of a ttk.LabeledScale raises an error. The same happens if the value is set after entering the mainloop.

Does not affect python 3.4.3. Does not affect ttk.Scale. No error is raised if you do not call mainloop.

import tkinter as tk
import tkinter.ttk as ttk
root = tk.Tk()
w = ttk.LabeledScale(root)
w.pack()
w.scale.set(1)
root.mainloop()

Traceback (most recent call last):
  File "d:\users\u938001\AppData\Local\Programs\Python\Python35-32\lib\tkinter\__init__.py", line 1550, in __call__
    return self.func(*args)
  File "d:\users\u938001\AppData\Local\Programs\Python\Python35-32\lib\tkinter\ttk.py", line 1540, in _adjust
    newval = self._variable.get()
  File "d:\users\u938001\AppData\Local\Programs\Python\Python35-32\lib\tkinter\__init__.py", line 355, in get
    return self._tk.getint(self._tk.globalgetvar(self._name))
TypeError: getint() argument must be str, not float

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "itcomp.py", line 8, in <module>
    root.mainloop()
  File "d:\users\u938001\AppData\Local\Programs\Python\Python35-32\lib\tkinter\__init__.py", line 1131, in mainloop
    self.tk.mainloop(n)
  File "d:\users\u938001\AppData\Local\Programs\Python\Python35-32\lib\tkinter\__init__.py", line 1554, in __call__
    self.widget._report_exception()
AttributeError: 'IntVar' object has no attribute '_report_exception'

[serhiy-storchaka]

This is caused by replacing int() by self._tk.getint() in IntVar.get() (bpo-23880). But the failure can be reproduced even in 3.4 if set tk.wantobjects = 0 before creating root widget.

One way is making getint() accepting floats. This fizes original example, but doesn't solve the issue for tk.wantobjects = 0.

Other way is making IntVar.get() falling back to integer part of getdouble(). This fixes the example in both modes. Proposed patch goes this way.

[python-dev]

New changeset 394b2b4da150 by Serhiy Storchaka in branch '3.5':
Issue bpo-27939: Fixed bugs in tkinter.ttk.LabeledScale and tkinter.Scale caused
https://hg.python.org/cpython/rev/394b2b4da150

New changeset 91884d043fdc by Serhiy Storchaka in branch '3.6':
Issue bpo-27939: Fixed bugs in tkinter.ttk.LabeledScale and tkinter.Scale caused
https://hg.python.org/cpython/rev/91884d043fdc

New changeset 9e3931aa1ff0 by Serhiy Storchaka in branch 'default':
Issue bpo-27939: Fixed bugs in tkinter.ttk.LabeledScale and tkinter.Scale caused
https://hg.python.org/cpython/rev/9e3931aa1ff0