[Python-3000] pre-PEP: Procedure for PEPs with Backwards-Incompatible Changes

[Steven Bethard]

On 3/27/06, Brett Cannon <brett at python.org> wrote:
> Requiring code that can identify things in 2.x that will change in 3.0
> that are coded externally from the interpreter is going to be *really*
> difficult in some situations, if not impossible to get right.  Just
> look at dict.items(); how do you do that?

You issue a warning for every .items() call.  If you want to be a
little more intelligent about it, you issue a warning to every
.items() call that isn't used directly in a for-loop.

Sure, it's going to generate false-positives[1], but the PEP says
that's okay.  At least in my own code, it wouldn't generate that many
false positives either -- most of my calls to items are on builtin
dicts.  Others who use a lot of custom dict-like objects would get
more, but the custom dict-like objects likely need upgraded to the
Python 3000 interface as well.

Maybe each PEP should have it's own flag to enable/disable the
warnings issued by python3warn.py?  Then after you'd checked all your
.items() calls (and presumably corrected them or determined they were
false-positives), you could ask python3warn.py to stop warning you.

Steve

[1] It's going to generate some false-negatives too, when someone's
done something like ``func = mydict.items``.  But we're never going to
get perfect warnings (unless people are crazy enough to want to
maintain the branch), so I'm willing to accept that.
--
Grammar am for people who can't think for myself.
        --- Bucky Katt, Get Fuzzy