[leobelle]

Twisted is a library you might want to use if you want to write non-blocking code. So you would care a great deal if this wasn't python 3 if you wanted to use python 3.

Mercurial is an application you use to version control your source. I'm not sure I understand why any python developer would care if Mercurial was written in python 2 as long as it worked. Maybe if someone was writing a Mercurial plugin or patching Mercurial they would care.

[nostrademons]

Python 3.4 comes with asyncio, which takes a lot of the ideas of Twisted but forward-ports them to the standard library with cleaner language support. So for new projects, Twisted shouldn't hold you back - just use the standard lib. For legacy Twisted projects that are thinking of porting it's still an issue.

[vertex-four]

Twisted contains a lot more than asyncio does. asyncio is the equivalent of Twisted's Reactors, which are the internal bits which manage the basics of the async event loop, watching file handles, etc; but Twisted contains a great many abstractions on top of that, not to mention the many protocol libraries.

Luckily, a Twisted Reactor can be built on top of asyncio, and this will likely happen as people port more parts of Twisted to Python 3 (it's a long-running project with fairly little interest from developers willing to put work into it).

Alternatively, people could start to build new libraries that implement all the abstractions and protocol implementations that Twisted has to offer. I think it'd be preferred that even if each abstraction/protocol were a separate repo and installable package, they'd all be under the same "banner", so that everything interoperates correctly and using the same set of abstractions.

[yeukhon]

Standard library doesn't always make things easier. We have urllib but do we recommend requests for doing http requests? So either Twisted is ported or someone else write a new Twisted-like (but simpler?). I know Guido doesn't like callback-style programming.

[pekk]

asyncio supports callback-style programming.

[yeukhon]

The point is some developers don't want to reinvent Twisted on their own. They like Python 3 and they want to keep up with Python 3 but they don't want to move away from Twisted. Just like I am asking you to write your own Django because half of the things to build Django is in standard library.

[yeukhon]

> I'm not sure I understand why any python developer would care

And you did say that some people - people who write plugins or develop Mercurial for living - do care later in your sentence. That's some developers. And the parent was asking whether Python 3 was safe to use. It's nice to know that some major Python projects are not ready for Python 3.

[erichurkman]

Outdated packages matter insofar as that you must maintain a working 2.x install alongside your 3.x if you use tools that need 2.x.

Hopefully these start disappearing, as Ubuntu and Arch have already moved to 3.x.

[leobelle]

This has very little to do with Python developers deciding between version 2.7 and 3.x. If you wrote a library or an app in Python 3.x packagers should require the appropriate version of Python as a dependency. Sam with v2. Developers shouldn't worry about that.