William Gill wrote:
> That does it!, thanks.
>
> Thinking about it, when I created a derived class with an __init__
> method, I overrode the base class's init. It should have been
> intuitive that I needed to explicitly call baseclass.__init(self), it
> wasn't. It might have hit me if the fault was related to someting in
> baseclass.__init() not taking place, but the recursion loop didn't give
> me a clue. Any idea why failing to init the base class caused the loop?
You never pasted the first part of the traceback:
File "<pyshell#204>", line 1, in -toplevel-
app.title('frob')
File "C:\Python24\Lib\lib-tk\Tkinter.py", line 1531, in wm_title
return self.tk.call('wm', 'title', self._w, string)
File "C:\Python24\Lib\lib-tk\Tkinter.py", line 1654, in __getattr__
return getattr(self.tk, attr)
File "C:\Python24\Lib\lib-tk\Tkinter.py", line 1654, in __getattr__
return getattr(self.tk, attr)
When you didn't call Tk.__init__(self), self.tk was never initialized.
Further, it's obvious from the traceback that Tk implements a
__getattr__ method; from the python docs:
__getattr__(self,name): Called when an attribute lookup has not found
the attribute in the usual places
Since self.tk doesn't exist, __getattr__(self,tk) was called. Without
looking at the TKinter source code, we can surmise that there's a
default behavior of "if self doesn't have it, return the relevant
attribute from within self.tk." The problem, of course, arises when
self.tk doesn't exist -- this causes the self.tk reference to call
self.__getattr__('tk'), which is recursive.
The infinite recursion, then, is a mild bug in TKinter that doesn't show
itself during normal use. The proper solution should be to replace the
self.tk call with either self.__dict__['tk'], or to make Tk a new-style
class and use object.__getattribute__(self,'tk'). (Note: there are
probably some fine details that I'm missing in this 'solution', so take
it with a potato-sized grain of salt. The general principle still
applies though.)
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