myths about python 3

Dino Viehland dinov at
Thu Jan 28 17:37:24 CET 2010

Stefan wrote:
> >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.)

I just want to echo this as I completely agree.  Last time I went through the
list it looked like there were around 10 major new features (some of them even
not so major) that we needed to implement to bring IronPython up to the 3.0
level.  It shouldn't be too time consuming, and it greatly improves our 
compatibility by finally having the same string types, but our users don't 
yet want us to stop supporting 2.x.

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