[Cython] [Python-Dev] Using Cython for standard library?

[Stefan Behnel]

Hi,

Robert Bradshaw wrote:
> On Nov 5, 2008, at 11:18 AM, Stefan Behnel wrote:
>> Robert Bradshaw wrote:
>>> I think the most immediate official milestone is being able to
>>> compile 100% of Cython code. This is the target for 1.0.
>> Did you really mean Cython here or Python? I think 100% Python is  
>> somewhat
>> hard to prove. I would expect that we are pretty close to compiling  
>> Py2.4
>> code, and a bit further from compiling 2.5 code (which mainly includes
>> generator expressions). Not sure about 2.6, which was a heavily  
>> moving target
>> last time I checked.
> 
> Sorry, I meant Python here. I'd say the goal is at a minimum to run  
> the entire Python regression suite for 2.x, probably 2.4 or 2.5.

Then runtests.py --sys-pyregr is your friend. :)

Note that this requires the Python test suite to be installed, which isn't the
case in a normal Python install (at least on most Linux distros). The best is
to build your own clean Python somewhere apart and use that.

If compiling Python is our first goal, I suggest that people get "sys-pyregr"
running on a Python 2.5 installation and fix tests. When a test fails
unexpectedly, I'd also suggest to check it again with Python 2.6, just to be
sure it didn't change behaviour.


>> If you meant Cython, this requires a stable definition of what the  
>> Cython language actually is.
> 
> Yeah, I'd certainly like to eventually move to a more stable (and  
> precise) definition than "whatever the compiler accepts at the  
> moment" :).

Yep, that's the state of the art. :)

IMHO, the definition is something in the lines of

Python 2.5
- some unsupportable features
+ some well defined C features
+ some additional features: buffer syntax, pure Python syntax, ...

Some of that is in the Wiki already.


> What is the timeline for Py2.7?

I don't think there is one yet, but I'd expect a beta by next summer, given
that 2.6 final is out, the developers are focussing on Py3.0 now, and 2.7/3.1
are expected to be cleanup releases.


> Also, if we migrate our source to  
> Py3, will that exclude running it under Py2? Will we have to maintain  
> two separate codebases?

I still hope that the 2to3 tool (or maybe a future 3to2 tool, as often
discussed) will help us here once we get the code clean enough. Plex is a
problem, for example, but not a major one either. I think the test suite is
good enough by now to give these things another try.


>>> One thing that is not clear is
>>> if a (sufficiently advanced?) user would be able to use the newer
>>> Cython with an older version of Python (say, if some projects/modules
>>> he needed weren't ported yet.)
>> I'm not sure where you see the problem here. A user wouldn't  
>> replace the core
>> Cython (i.e. everything else would keep working), but import a  
>> separate Cython
>> install instead.
> 
> If it could hook in an "hijack" the builtin one, especially if  
> there's tighter integration of the latter, then that would be very cool.

PyXML did that with the stock Python XML support - although not very
beautifully. So, yes, there are ways to do these things. We will just have to
find one that users can live with.

Stefan