Python modules not updating after restarting the main module.

Question

I've recently come back to a project having had to stop for about 6 months, and after reinstalling my operating system and coming back to it I'm having all kinds of crazy things happen. I made sure to install the same version(2.6) of python that I was using before.

It started by giving me strange tkinter error that I hadn't had trouble with before, the program is relatively simple and the 2 or 3 bugs that were left when i quit, I had documented and weren't related to the interface.

Things got even weirder when the same error would pop up even after I had removed the offending section of code. In fact, the traceback pointed to a line that didn't even exist in the module it was referencing, eg: line 262 when the module was only 200 lines long.

After just starting a completely new file for the main module and copy/pasting it finally recognized that the offending code was gone and I stopped getting the error only to find that any updates to the code I made in another module didn't show up when I restarted the program through the shell. (I didn't forget to save.) After fiddling with this, of course, the old interface error came back, only in a different section of code that had been working previously.

In fact, if I revert back to the files I had six months ago, the program works fine. As soon as I change anything in the main module, however, the interface bug comes back.

Here's the original error:

Exception in Tkinter callback
Traceback (most recent call last):
  File "C:\Python26\lib\lib-tk\Tkinter.py", line 1410, in __call__
return self.func(*args)
  File "C:\PyStuff\interface.py", line 202, in dispOne
__main__.top.destroy()
  File "C:\Python26\lib\lib-tk\Tkinter.py", line 1938, in destroy
    self.tk.call('destroy', self._w)
TclError: can't invoke "destroy" command:  application has been destroyed

I'm guessing something else is going on here other than my own poor programming. Anyone have any ideas?

Edit: Thinking back, I believe I read something about it being a bad idea to run Tkinter programs through IDLE's shell, and it appears, at least, that the TclError has vanished if I instead start the main module by double clicking the .pyc file. Perhaps my problems were just a combination of that plus the timestamp/PYTHONPATH issues mentioned below by Chris Atlee and Vlad?

Answer 1

Check your PYTHON_PATH variable, you probably have an older version of the file.

Also start your python interpreter and type the following commands to check the path:

import sys
print sys.path

Take a careful look at the output and make sure you don't have any old directories sitting there.

Answer 2

I've had something similar happen. The cause for my problems was that my source control software (hg) was setting the date of files to a date in the past. Because of this, python chose to use previously generated .pyc files which had newer timestamps.

The solution was to delete all the .pyc files before testing the code.