[Python-Dev] Patch: AttributeError and NameError: second attempt.

[Martin v. Loewis]

[thread moved, since I can't put in proper References headers, anyway,
 just by looking at the archive]
> 1) I rewrite the stuff that went into exceptions.py in C, and stick it
>   in the _exceptions module.  I don't much like this idea, since it 
>   kills the advantage noted above.

>2) I leave the stuff that's in C already in C.  I add C __str__ methods 
>   to AttributeError and NameError, which dispatch to helper functions
>   in the python 'exceptions' module, if that module is available.

>Which is better, or is there a third choice available?

There is a third choice: Patch AttributeError afterwards. I.e. in
site.py, say

_AttributeError_str(self):
  code

AttributeError.__str__ = _AttributeError_str

Guido said
> This kind of user-friendliness should really be in the tools, not in
> the core language implementation!

And I think Nick's patch exactly follows this guideline. Currently,
the C code raising AttributeError tries to be friendly, formatting a
string, and passing it to the AttributeError.__init__. With his patch,
the AttributeError just gets enough information so that tools later
can be friendly - actually printing anything is done in Python code.

Fred said
>   I see no problem with the functionality from Nick's patch; this is
> exactly te sort of thing what's needed, including at the basic
> interactive prompt.

I agree. Much of the strength of this approach is lost if it only
works inside tools. When I get an AttributeError, I'd like to see
right away what the problem is. If I had to fire up IDLE and re-run it
first, I'd rather stare at my code long enough to see the problem.

Regards,
Martin