[Python-Dev] Dict suppressing exceptions

[Michael Chermside]

Michael Urman writes:
> I strongly believe that unicode vs str here is the symptom and not the
> actual problem. The comparison between two non-us-ascii str/unicode
> instances is but one of many ways to raise an exception during
> comparison.
       [... example ...]
> Yes this is made up code. But I'm not arguing for a feature; I'm
> arguing for backwards compatibility. Because we do not know where
> these legitimate uses are, we cannot evaluate their likelihood to
> exist nor the level of breakage they will cause. If we make this a
> warning for any exception, we can satisfy both imagined camps. Those
> in Armin's position can make that warning raise an exception while
> debugging, and those using it on purpose can squash it.

See also my example from the beginning of this thread
(http://mail.python.org/pipermail/python-dev/2006-August/067978.html).
The example wasn't from real code, but it WAS quite plausible --
straightforward use of a popular Python Cookbook recipe.

But we seem to have reached a rough consensus:

Later, Guido writes:
> How about we change unicode-vs-str __eq__ to
> issue a warning (and return False) instead of raising
> UnicodeException?
      [... Marc-Andre Lemburg agrees ...]
> Great! Now we need someone to volunteer to write a patch (which should
> include doc and NEWS updates) in time for beta 3 (Aug 18).

I don't *strongly* object to this consensus, but if you haven't
glanced at my original example, take a look - it might convince you.
The proposed solution will not help with my example. I'm not sure the
motivation for breaking code like that example -- the bug-hunting
motivation is satisfied by issuing a warning as Michael Urman proposes,
then use an exception after one more release when people have had time
to fix their code.

-- Michael Chermside