[Python-Dev] 3to2 Project

[Jesse Noller]

On Mon, Mar 30, 2009 at 12:37 PM, Collin Winter <collinw at gmail.com> wrote:
> On Mon, Mar 30, 2009 at 7:44 AM, Jesse Noller <jnoller at gmail.com> wrote:
>> During the Language summit this past Thursday, pretty much everyone
>> agreed that a python 3 to python 2 tool would be a very large
>> improvement in helping developers be able to write "pure" python 3
>> code. The idea being a large project such as Django could completely
>> cut over to Python3, but then run the 3to2 tool on the code based to
>> continue to support version 2.x.
>>
>> I raised my hand to help move this along, I've spoke to Benjamin
>> Peterson, and he's amendable to mentoring a GSoC student for this
>> project and he's  already received at least one proposal for this.
>>
>> Additionally, there's been a number of developers here at PyCon who
>> are more than ready to help contribute.
>>
>> So, if people are interested in helping, coordinating work/etc - feel
>> free to sync up with Benjamin - he's started a wiki page here:
>>
>> http://wiki.python.org/moin/3to2
>
> If anyone is interested in working on this during the PyCon sprints or
> otherwise, here are some easy, concrete starter projects that would
> really help move this along:
> - The core refactoring engine needs to be broken out from 2to3. In
> particular, the tests/ and fixes/ need to get pulled up a directory,
> out of lib2to3/.
> - Once that's done, lib2to3 should then be renamed to something like
> librefactor or something else that indicates its more general nature.
> This will allow both 2to3 and 3to2 to more easily share the core
> components.
> - If you're more performance-minded, 2to3 and 3to2 would benefit
> heavily from some work on the pattern matching system. The current
> pattern matcher is a fairly simple AST interpreter; compiling the
> patterns down to pure Python code would be a win, I believe. This is
> all pretty heavily tested, so you wouldn't run much risk of breaking
> it.
>

A second note on performance, is that Benjamin was about to checkin a
version of 3to2 which used multiprocessing to help speed it up a bit -
he had to catch a plane, so he should have it done some time shortly.

-jesse