[eeZi]

Lots of incentives for us:

- clean Unicode support which prevents mistakes which used to bite us in production

- native async syntax, compatible with Tornado

- asynchronous generators (yield from a coroutine!)

- pathlib and os.scandir

- type annotations

- matrix multiplication

- chained exceptions

- faster dicts, ordered by default

So many useful features, and with the latest Python 3 releases porting has become really easy thanks to improved compatibility with the old syntax.

[icegreentea]

They are all pluses, but most of those didn't exist till the last couple years. So effectively the first 6 or so years of Python 3 existing had much less incentive.

I think the flip around - ~30% adoption of a newest version at 1-2 years in - especially one that breaks backwards compatibility isn't bad.

I've started numerous python projects at work over the last year all on 2.7. I think we just started the last one. We're finally ready to jump to 3.

[dr_zoidberg]

Indeed, and ordered dicts come from Py 3.6, which is in beta now and expected for December.

If async and this had been in Py3 from the start, they could've done a far better argument saying "hey, we broke all this stuff, but you get asyinc I/O and faster dicts" (a note of faster dicts: since many classes and language mechanisms use dicts, it should have an encompassing effect on all of python performance -- maybe not 30% or 40% faster, but a few % all around, which is kind of what micro benchmarks are showing with 3.6 betas)

[est]

All of these incentives you listed are also doable in Py2k.

[poooogles]

Native Async syntax won't be doable in Python 2.

[est]

We have gevent, tornado, twisted, pyuv.