Benjamin Kaplan, 27.01.2010 22:25: > On Wed, Jan 27, 2010 at 3:56 PM, John Nagle <na...@animats.com> wrote: >> 2. Python 3 is supported by multiple Python implementations. >> >> FALSE - Only CPython supports 3.x. Iron Python, Unladen Swallow, >> PyPy, and Jython have all stayed with 2.x versions of Python. >> > When Python 2.6 came out, Jython was still on 2.2. The difference > between 2.2 and 2.6 is almost as big of a difference as between 2.6 > and 3.0.
>From an implementors point of view, it's actually quite the opposite. Most syntax features of Python 3 can be easily implemented on top of an existing Py2 Implementation (we have most of them in Cython already, and I really found them fun to write), and the shifting-around in the standard library can hardly be called non-trivial. All the hard work that went into the design of CPython 3.x (and into its test suite) now makes it easy to just steal from what's there already. The amount of work that the Jython project put into catching up from 2.1 to 2.5/6 (new style classes! generators!) is really humongous compared to the adaptations that an implementation needs to do to support Python 3 code. I have great respect for the Jython project for what they achieved in the last couple of years. (I also have great respect for the IronPython project for fighting the One Microsoft Way into opening up, but that's a different kind of business.) If there was enough interest from the respective core developers, I wouldn't be surprised if we had more than one 'mostly compatible' alternative Python 3 implementation in a couple of months. But it's the obvious vicious circle business. As long as there aren't enough important users of Py3, alternative implementations won't have enough incentives to refocus their scarce developer time. Going for 2.6/7 first means that most of the Py3 work gets done anyway, so it'll be even easier then. That makes 2.6->2.7->3.2/3 the most natural implementation path. (And that, again, makes it a *really* good decision that 2.7 will be the last 2.x release line.) >> 3. Python 3 is supported by most 3rd party Python packages. >> >> FALSE - it's not supported by MySQLdb, OpenSSL, feedparser, etc. >> >> Arguably, Python 3 has been rejected by the market. Instead, there's >> now Python 2.6, Python 2.7, and Python 2.8. Python 3 has turned into >> a debacle like Perl 6, now 10 years old. > > Give the package maintainers time to update. There were some pretty > big changes to the C API. Most of the major 3rd party packages like > numpy and MySQLdb have already commited to having a Python 3 version. > They just haven't gotten them out yet. I second that. NumPy has already announced that they'll rewrite some of their code in Cython to make it more maintainable and portable (and to simplify the port to Py3, I guess). Other projects will equally well find their ways to get their code ready. It's just a matter of time. I think there's enough pressure on the maintainers by now (both from users and from personal pride) to consider their packages tainted if they aren't portable enough to run on all major (C)Python versions (and Py3.1 certainly is one of them), even if they don't use them themselves. That appears to be an impressively good incentive. Stefan -- http://mail.python.org/mailman/listinfo/python-list
