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

[Aahz]

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.
-- 
Aahz (aahz at pythoncraft.com)           <*>         http://www.pythoncraft.com/

Weinberg's Second Law: If builders built buildings the way programmers wrote 
programs, then the first woodpecker that came along would destroy civilization.