Ask for help about a tkinter problem

Sun Aug 20 05:51:40 EDT 2017

jfong at ms4.hinet.net wrote:
> I am running a tkinter tutor downloaded from web,
> https://github.com/daleathan/widget-tour-py3. there are two files
> involved:
>> --------------------
> #file button.py
>> from tkinter import *
> from tkinter.ttk import *
> import infrastructure
> ...
> class ButtonsDemoWindow( infrastructure.DemoWindow ):
> ...
> def __init__( self ):
> ...
> ...
> for c in ('Peach Puff', 'Light Blue', 'Sea Green', 'Yellow' ):
> b = Button(self.frame, text=c)
> b['command'] = infrastructure.callit( self.callback, c )
> b.pack( side=TOP, expand=YES, pady=2 )
>> def callback(self, color):
> self.frame['background']=color
>> def runDemo():
> ButtonsDemoWindow()
>> ----------------------
> #file infrastructure.py
> ...
> class DemoWindow( Toplevel ):
> ...
> ...
> class callit:
> def __init__(self, function, *args ):
> self.f = function
> self.args = args
>> def __call__(self, *ignored):
> self.f( *self.args)
>> --------------------
> I run it under the DOS box:
>> D:\Works\Python\widget-tour-py3-master>python
> Python 3.4.4 (v3.4.4:737efcadf5a6, Dec 20 2015, 19:28:18) [MSC v.1600
> 32 bit (Intel)] on win32 Type "help", "copyright", "credits" or
> "license" for more information.
> >>> import button
> >>> button.runDemo()
>> after the window shows up, I pressed one of the buttons and get the error
> below:
>>>>> Exception in Tkinter callback
> Traceback (most recent call last):
> File "C:\Python34\lib\tkinter\__init__.py", line 1538, in __call__
> return self.func(*args)
> File "D:\Works\Python\widget-tour-py3-master\infrastructure.py", line
> 216, in __call__
> self.f( *self.args)
> File "D:\Works\Python\widget-tour-py3-master\button.py", line 39, in
> callback
> self.frame['background']=color
> File "C:\Python34\lib\tkinter\__init__.py", line 1331, in __setitem__
> self.configure({key: value})
> File "C:\Python34\lib\tkinter\__init__.py", line 1324, in configure
> return self._configure('configure', cnf, kw)
> File "C:\Python34\lib\tkinter\__init__.py", line 1315, in _configure
> self.tk.call(_flatten((self._w, cmd)) + self._options(cnf))
> _tkinter.TclError: unknown option "-background"
>>> When I looked into the file tkinter\__init__.py, I found there is codes
> which add conditionally a '-' onto the original cnf argument:

That is just a peculiarity of TCL; a "-" is added to the option by the 
Python wrapper before passing it along
 
> 1305 def _configure(self, cmd, cnf, kw):
> 1306 """Internal function."""
> ...
> ...
> 1313 if isinstance(cnf, str):
> 1314 return self._getconfigure1(_flatten((self._w, cmd,
> '-'+cnf)))
>> Is it the reason this exception raised? Why is that?

I can confirm the problem. It looks like the bug was introduced when the 
example was converted from stock tkinter to the new ttk widget set.
While
frame["background"] = color
works when frame is a tkinter.Frame widget the newer tkinter.ttk.Frame 
widget uses "styles" to configure its appearance. 
I have not used that new feature, but with the help of
http://infohost.nmt.edu/tcc/help/pubs/tkinter/web/ttk-style-layer.html
and some trial and error I modified the example to use a style:
$ diff -u button.py button_fixed.py

--- button.py 2017年08月20日 11:44:33.841839812 +0200
+++ button_fixed.py 2017年08月20日 11:44:04.032426163 +0200
@@ -25,7 +25,9 @@
 
 infrastructure.DemoWindow.__init__(self, intro, 'button.py' )
 
- self.frame=Frame(self)
+ self.style = Style(self)
+ self.frame=Frame(self, style="foo.TFrame")
+
 self.frame.pack(expand=YES, fill=BOTH )
 for c in ('Peach Puff', 'Light Blue',
 'Sea Green', 'Yellow' ):
@@ -36,7 +38,7 @@
 
 
 def callback(self, color):
- self.frame['background']=color
+ self.style.configure("foo.TFrame", background=color)
 
 
 def runDemo():
$ 
However, I'm not sure if this is the canonical way to write it...
