[Tkinter-discuss] A Button command callback question...

[Michael Lange]

Hi,

Thus spoketh GKalman <kalman_g at msn.com> 
unto us on Sun, 17 Jul 2011 20:34:22 -0700 (PDT):

> 
> The following code fragment works OK.  Question: why?
> #======================================
> from Tkinter import *
> root=Tk()
> 
> lbl=Label(root,text='1').pack()
> 
> def doIt():
>     lbl.config(bg="yellow")
> 
> btn=Button(root,text="do", bg="cyan",command=doIt).pack()
> 
> root.mainloop()
> #=======================================
> My question is: how is the instance lbl.config(...) recognized in the
> doIt callback fn when called from the main w/o an argument referencing
> lbl?

When I run this example and hit the button I get:

Exception in Tkinter callback
Traceback (most recent call last):
  File "/usr/lib/python2.6/lib-tk/Tkinter.py", line 1413, in __call__
    return self.func(*args)
  File "test6.py", line 8, in doIt
    lbl.config(bg="yellow")
AttributeError: 'NoneType' object has no attribute 'config'

as one would expect.

Regards

Michael


.-.. .. ...- .   .-.. --- -. --.   .- -. -..   .--. .-. --- ... .--. . .-.

	"What happened to the crewman?"
	"The M-5 computer needed a new power source, the crewman merely
got in the way."
		-- Kirk and Dr. Richard Daystrom, "The Ultimate Computer",
		   stardate 4731.3.