[Python-Dev] Gradual migration

[Guido van Rossum]

> Paul Prescod wrote:
> > 
> > Python 3K. It is the repository for our hopes and dreams. We tend to
> > invoke it in three different situations:
> > 
> >  1. in delaying discussions of gee-whiz features (e.g. static type
> > checking)
> > 
> >  2. in delaying hairy implementation re-factoring that we don't
> > want to undertake right now.
> > 
> >  3. in delaying painful backwards-compatibility breakage
> > 
> > I think it is somewhat debatable whether we really need to or should do
> > these three things all at once but that's a separate discussion for
> > another day. (the other experiment may inform our decision)

Marc-Andre Lemburg replied:

> I think will simply be a consequence of doing a complete rewrite
> of the interpreter for Py3K. AFAIR, the only truely feasable
> solution would be doing the rewrite in a widely portable
> subset of C++ and then managing classes at that level.
>  
> Moving to a common and very low-level strategy for classes
> will allows us to put even the most basic types (strings and
> numbers) into an inheritence tree. 
> 
> Differences like the
> ones between Unicode and 8-bit strings would then flesh
> out as two different subclasses of a generic string type which
> again is based on a generic sequence type.
> 
> The same could be done for dictionaries: special ones for
> just string keys, case insensitive lookups, etc. could all
> be subclasses of a generic mapping class.
> 
> Dito for numbers (and division strategies).
> 
> By following this principle there won't be all that much
> breakage, since the old functionality will still be around,
> only the defaults will have changed.
> 
> Add to this pluggable compilers and ceval loops, plus a nice
> way of configuring the lot on a per-module basis and you're
> set. (Ok, it's a fluffy clouds image, but you get the picture ;-)

Good job in channeling me, Marc-Andre!  I'm sure that's not exactly
how it's going to be, but on the face of it, this sure sounds like a
reasonable possible route.  Do you want to be the author for PEP-3000?

--Guido van Rossum (home page: http://www.python.org/~guido/)