[Python-ideas] Proposal: Moratorium on Python language changes

Brett Cannon brett at python.org
Fri Oct 23 04:06:24 CEST 2009

On Thu, Oct 22, 2009 at 18:22, Jim Jewett <jimjjewett at gmail.com> wrote:

> On Thu, Oct 22, 2009 at 3:08 PM, Guido van Rossum <guido at python.org>
> wrote:
> > Anyway, the "Python core" includes a lot of stuff that isn't covered
> > by the moratorium (which only prohibits changes to syntax and
> > associated semantics, not implementation issues).
> Changes to semantics are rare enough that I'm not sure a moratorium
> (but allowing bug fixes) would matter.  (Particularly if you stick to
> the claim that details of import resolution are
> implementation-specific.)
> I have no opinion on changes to syntax; they're already uncommon, but
> saying they'll wait until 2013 doesn't bother me.
> The limit on builtins may be more of a problem.  For example, I liked
> Brett's work on signatures. If he gets motivated to work on it again,
> I don't want him to say "Drat; I really need access to this one extra
> function attribute, which isn't currently exposed at the python level.
>  I guess I'll have to wait a few years."
Since my PEP 362 keeps (surprisingly) coming up), I will use it as an

If the code actually gets checked in then chances are it will be put into
inspect first to work out any details. If it happens to receive uptake, it
can get pushed up to a built-in or something when the moratorium is lifted.
But assigning to __signature__ or something on functions is not really
covered by this as anyone could do that on their own w/o changing Python.
What would be gray area is if help() was changed to recognize the attribute.
But that could potentially be negotiated as implementation detail.

> It would be reasonable to say that changes to builtins will be rare,
> and will typically be strictly additions to functionality, as though
> they were replaced by a subclass which overrode nothing except that
> certain Exceptions were now handled internally.  (In other words, *if*
> the name previously existed, it either keeps the same meaning, or gets
> wrapped in something that just calls the old meaning as a try suite,
> with all new functionality inside the except suite.)

I still prefer Guido's hard-line on changes and we don't even do additions.

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