[sandGorgon]

i keep looking for a reason to switch to python 3 and cant find one. Plus if I want to use the cool stuff in Pypy.. then I better not !

overall - very less reason to consider Py3 at all. Performance would have been one - if there were a comparison between gevent and asyncio.

[mrweasel]

>i keep looking for a reason to switch to python 3 and cant find one.

Unicode? Not having to deal with encoding all over the place has been well worth switch to Python 3. If performance is a a huge issue, I honestly don't know why you would stay on Python (regardless of version)

I wouldn't want to switch back to Python 2.7 is I can avoid it. There's honestly no reason not to go with 3.4 or 3.5 at this point, unless you happen to have a large Python 2 code base.

[sago]

This is a superficially trivial bit of syntactic sugar, but an example of the way small tweaks can provide big impact. This:

    > do_something(*some_args, *some_more_args)

is rocking my world right at the moment. That's a massive time saving feature I've been waiting for and worth the price of a 3.5 upgrade.

[kenneth_reitz]

Oh cool, I didn't know about this!

[coldtea]

>If performance is a a huge issue, I honestly don't know why you would stay on Python (regardless of version)

I see this a lot. That one doesn't care of performance that much to switch to, say, C++ or Go, doesn't mean one is OK with regressions to what they currently use.

[rdtsc]

I see you've been downvoted. Interesting, you said that you haven't found a reason to switch and someone looked at it and thought "How dare you not find a reason to switch, here let's teach you a lesson".

But in large I agree. 3 hasn't provided enought of a carrot and 2 hasn't been enough of a pain for many people to want to switch. Especially when it comes to existing stable code bases. For new development, yes, many can and should pick Python 3. But if say Python 3 brought even a 20% speed improvement overwall, the move would have been a lot faster.

I find people are ok with accepting some breakages due to re-writes if either existing stuff is very broken, or new stuff is so much better.

[sandGorgon]

but Python 3 is not really an upgrade is it ? it is a very different language and most people who are pushing (downvoting?) for Python 3 dont seem to understand that.

I have zero problems with Python 3 per se - but when the vast majority of the ecosystem is on Py2 and there is no difference in performance... then I see no reason to consider any breakages.

[BuckRogers]

I think over time watching this behavior like the downvotes you received, I've figured it out. The idea is that newer folks come into Python, many don't want to learn the dominant version in effort to focus on the future as they understand it. So 2 continuing to live is viewed as a threat to that investment. Even though the two aren't that different and shouldn't matter which one you use, that isn't a popular point to bring up. It's a bit of a "newer version is always better" trap. That's true in general for software like a web browser, but not true for programming languages if they contain breaks or gain feature bloat (both are Python3 flaws). Conservative languages in both of those regards, are usually held in higher regard. It's also not a zero-sum game where for 3 to succeed, 2 must fail. Not that this is ever going to happen anyway. Thanks to how the PSF and associated handled this, the Python3 mistakes were never corrected. We're stuck with a permanent split for a long time as a result. It's tragic really, coming from someone who programs in Python daily. There are many ways to resolve it too, but the CPython core dev team refuse to consider any of them.

As a result, guys like you who are thinking rationally become the problem for being 'lazy' (acting in your own best interests which is exactly what everyone is doing) and are the enemy. People, especially newcomers, get tired of waiting for Python2 to 'die' and instead of put the onus on those who made the mistakes with Python3 (they've stuck it out, refusing to correct their own mistakes because that's more work), it becomes twisted and you are now the problem in their mind. Even though you were probably a part of what made Python successful to begin with. Amazing how that pans out, right?

Usually these illusions go away once a full time job is found, there are some but the vast majority are companies with big Python2 codebases that have features to deliver. If they move services anywhere from CPython it's to PyPy for the performance gain.

[eeZi]

Nah. I'm a long-time Python developer (10 years+) and I moved everything over to Python 3 because there are so many advantages. This includes a number of massive internal code bases that I maintain at my day job. Porting is surprisingly easy nowadays, it used to hurt a lot more.

Management is fine with development time spent on migrating to Python 3, since it's an investment in the future (Python 2 will be EOL in 2020!).

[BuckRogers]

Sounds like you're a lone wolf at a smaller company. Different ballgame from the "longtime Python devs" that I'm talking about. I had an employer with a 500KLOC Python2 codebase, a billion dollar business on the line, and new features to deliver. That 2020 date is just a big political stunt. As was 2015 or it wouldn't have been a snap of the fingers to extend it. Code won't stop working in 2020 and security is largely handled by a webserver.

I use Python3 sometimes as well, but doesn't mean what I'm saying isn't true.

[eeZi]

It is NOT a different language. It's not backwards compatible, sure, but usually, only minor changes are required and 2to3 helps a lot. At this point, pretty much all of the libraries are ported and their API stays the same. The libraries which haven't been ported yet are either notable exceptions (Twisted!) or are unmaintained.

Very helpful for porting: http://python-future.org

[eeZi]

A few reasons which made me switch:

  - Python 2 will be EOL in 2020, that's four years

  - vastly improved Unicode support

  - a number new libraries are Python 3 only

  - asyncio and the new async syntax

  - exception chaining (!)

  - type annotations

  - lots of improvements all over the place

[sandGorgon]

Python 2 will not be EOL in 4 years. Not with the billions of lines of code out there. If the Python foundation dares to do this, it will create a fork. Probably even funded by Dropbox, Google and the like.

I wont dispute you on any other aspects - except two. have you tried using gevent versus asyncio ? gevent is running in production at several of the largest API services in the world. Asyncio is not yet deployed at this scale.

Second about new libraries being python 3 only - really dispute that. In fact its the other way around. For example, the brand new Tensorflow library (which google uses in production for its own AI) was released on Python 2 only .. and Python 3 support was later patched in. This is the case with every new library of consequence that I'm seeing.

[eeZi]

The Python foundation won't budge on the 2020 EOL date, for sure. RedHat will support it until RHEL 7 is EOL (~2027), but that's security/critical fixes only - while Python 3 gets all the new features and development efforts.

At some point, the opportunity cost of staying with Python 2.7 is higher than the one-time effort of porting everything to Python 3, so companies will move. Especially the likes of Google and Dropbox.

gevent vs. asyncio - sure, gevent is more mature. But asyncio is undoubtedly the better/nicer API. asyncio's explicit await syntax is much nicer than gevent's implicit monkey-patching, which makes it harder to reason about the code.

Tensorflow isn't really a new library, it was only recently open sourced.

As for Python 3-only libraries:

- https://pypi.python.org/pypi?:action=browse&show=all&c=595

- https://github.com/aio-libs

Also note that Django will drop Python 2 support in time with the Python 2 EOL: https://www.djangoproject.com/weblog/2015/jun/25/roadmap/

Also, many new Python-based open source projects are Python 3 only.

[takeda]

This is wishful thinking.

There's a cost to maintain, and that's why PSF is moving to 3. I'm sure if Google and/or Dropbox would pay, PSF might continue maintenance[1].

Anyway the issue here is that you won't get any new features in python 2.7, and that already happened last year, currently python 2 only gets security fixes.

> have you tried using gevent versus asyncio ? gevent is running in production at several of the largest API services in the world. Asyncio is not yet deployed at this scale.

Both of them are available on python 3. On python 2 you can't chose. AsyncIO strength is that it is integrated into the language. Especially in 3.5 you have a new syntax to use it, no need to install new libraries, no need to compile anything. No monkey patching. Also AsyncIO is more generalized and could be adapted to other tasks, not necessarily for asynchronous calls.

[1] In fact surely Red Hat will continue to maintain it until 2027 since they decided to ship it with Red Hat 7, but question is whether they will share it with general users, or will they only provide it to paying customers.

[haimez]

It seems ridiculous (to me, someone that is superficially aware of the python ecosystem but not a real user) that they haven't tried to find a way to incentivize people to switch with a real carrot. For example: removing the GIL.

Running out the clock on waiting for library support to become mostly python 3 is inevitable, but so far has been slower than molasses.