[Python-ideas] Put default setstate and getstate on object for use in coöperative inheritance.

[Neil Girdhar]

I understand your concern for cpython, but I don't think it will be the
future of Python.  I think every object should have a dict and then the JIT
should just make it fast.  I think that's possible.

Anyway, this is a separate discussion.  My new proposal is for setstate and
getstate to have default implementations that first check for the __dict__
attribute and do the normal thing (getstate returns {}, setstate does
nothing) if it doesn't exist.

Best, Neil


On Sat, Jun 7, 2014 at 5:34 AM, Nick Coghlan <ncoghlan at gmail.com> wrote:

> On 7 June 2014 18:46, Neil Girdhar <mistersheik at gmail.com> wrote:
> >
> > Right, that makes sense.  I think the flyweight pattern would eliminate
> > this: use a special representation for the common case and then switch
> to a
> > real representation as soon as things become weird.  (I can see how that
> > would be extra development time unless it could be done automatically by
> a
> > clever JIT.)
>
> The flyweight pattern imposes its own costs in terms of additional
> levels of indirection and even more pointers to carry around. The
> approach we take is that object instances get a __dict__ attribute by
> default, unless the creator of the class decides "there are going to
> be enough of these for it to be worth skipping the space not only for
> the attribute dicts themselves, but also for the attribute dict
> reference on each instance". We do the same with weakref support.
>
> The other thing to keep in mind is that many of CPython's "internal"
> representations aren't actually internal: many of them are exposed in
> various ways through the CPython C API. As other implementations have
> discovered, preserving full compatibility with that API places some
> pretty significant constraints on the implementation techniques you
> use (or else means putting a lot of work into a compatibility shim
> layer like IronClad, JyNI or cpyext).
>
> Cheers,
> Nick.
>
> --
> Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/python-ideas/attachments/20140607/6fd3235e/attachment.html>