Ask for help about a tkinter problem

[jfong at ms4.hinet.net]

Peter Otten at 2017/8/20 UTC+8 PM 5:52:24 wrote:
> 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   2017-08-20 11:44:33.841839812 +0200
> +++ button_fixed.py     2017-08-20 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...

Thank you for your answer. I try not to use the ttk by comment the line "from tkinter.ttk import *", and also try your "Style" modification codes, both work:-)

> That is just a peculiarity of TCL; a "-" is added to the option by the
> Python wrapper before passing it along

This extra "-" confuses people when showing up in the Traceback info. Can't figure out why the author want to do this.

--Jach