[Python-Dev] Choosing a best practice solution for Python/extension modules

[Brett Cannon]

On Sat, Feb 21, 2009 at 20:12, Aahz <aahz at pythoncraft.com> wrote:

> On Sat, Feb 21, 2009, Brett Cannon wrote:
> > On Sat, Feb 21, 2009 at 15:46, Aahz <aahz at pythoncraft.com> wrote:
> >> On Sat, Feb 21, 2009, Brett Cannon wrote:
> >>>
> >>> I am seeing two approaches emerging. One is where pickle contains all
> >>> Python code and then uses something like use_extension to make sure
> >>> the original Python objects are still reachable at some point. This
> >>> has the drawback that you have to use some function to make the
> >>> extensions happen and there is some extra object storage.
> >>>
> >>> The other approach is having pickle contain code known not to
> >>> be overridden by anyone, import _pypickle for stuff that may be
> >>> overridden, and then import _pickle for whatever is available. This
> >>> approach has the perk of using a standard practice for how to pull in
> >>> different implementation. But the drawback, thanks to how globals are
> >>> bound, is that any code pulled in from _pickle/_pypickle will not be
> >>> able to call into other optimized code; it's a take or leave it once
> >>> the call chain enters one of those modules as they will always call
> >>> the implementations in the module they originate from.
> >>
> >> To what extent do we care about being able to select Python-only on a
> >> per-module basis, particularly in the face of threaded imports?  That
> is,
> >> we could have a sys.python_only attribute that gets checked on import.
> >> That's simple and direct, and even allows per-module switching if the
> >> application really cares and import doesn't need to worry about threads.
> >>
> >> Alternatively, sys.python_only could be a set, but that gets ugly about
> >> setting from the application.  (The module checks to see whether it's
> >> listed in sys.python_only.)
> >>
> >> Maybe we should move this discussion to python-ideas for now to kick
> >> around really oddball suggestions?
> >
> > This is all about testing. If a change is made to some extension code it
> > should be mirrored in the Python code and vice-versa.
>
> Okay, I don't see how that is a response to my suggestion -- I can
> imagine that someone might want to test a combination of pure-Python and
> binary libraries.
>

I don't want to move it because this isn't some idea for a new feature that
may or may not be useful; this isn't an "idea", it's needed.

-Brett
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