[Python-Dev] [compatibility-sig] do all VMs implement the ast module? (was: Re: AST optimizer implemented in Python)

[Guido van Rossum]

On Mon, Aug 13, 2012 at 1:05 PM, fwierzbicki at gmail.com
<fwierzbicki at gmail.com> wrote:
> On Mon, Aug 13, 2012 at 12:06 PM, Brett Cannon <brett at python.org> wrote:
>>> I see nothing about ast possibly being CPython only. Should there be?
>>
>>
>> Time to ask the other VMs what they are currently doing (the ast module came
>> into existence in Python 2.6 so all the VMs should be answer the question
>> since Jython is in alpha for 2.7 compatibility).

[Jython]
> 2.5+ contains an ast.py that I obsessively compared to CPython's 2.5
> ast.py.

But CPython's ast.py contains very little code -- it's all done in ast.c.

Still, I'm glad you are actually considering this a cross-language
feature, and I will gladly retract my warning. (Still, I don't know if
it is subject to the usual backward compatibility constraints.)

> I haven't applied the same obsessiveness to 2.7, but I do
> intend to look closely at Jython's ast.py results compared to
> CPython's in the 3.x effort. Also I plan to allow some backwards
> compatibility compromises between early point releases of our 2.7
> series, as I want to apply what I learn in our 3.x effort to 2.7 point
> releases, so we should be able to keep up with most simple ast.py
> changes. I'm not so sure that the current discussion are going to be
> "simple though" :) -- if it's pure python we should hopefully be
> alright.

It might be pure python for Jython, but it's not for CPython.

-- 
--Guido van Rossum (python.org/~guido)