What versions of Python are in current use, and packages should support?

As a small-time Python p开发者_开发问答ackage writer (cobs, simplerandom), I'm wondering what Python versions I should support.

I've heard anecdotally that Python 2.5 is still in use on enterprise type servers. So I thought 2.5 was the oldest that needed to be practically supported, here in 2011.

However, I saw this blog in which the author says he's still using 2.4. From memory, I saw an e-mail on the PyCrypto mailing list saying they aimed to keep support going back to 2.2 if possible.

Of course, then there's Python 3.x which is slowly gaining momentum. It would be good to know who is using that.

Then, there is also Jython and Ironpython, and I have very little idea about them.

Is there any concrete and up-to-date Python installation/usage data available to enlighten us? Is there any "best practices" or other advice for what versions/flavours of Python a package writer should aim to support?

I think that this is a problem that's simply inherent when developing any software. Anyone could be running any version and would need support for that version (I wonder how many people are still running Windoze ME out there? ;)). Personally, when developing libraries, I'll support only support the current version+. If for no other reason, because I'm only one person and I don't have a team.

Having said that, I'd stick my packages up on github and take patches from anyone who wants support for previous versions (and is willing to put in the work).

Edit:

I've found that a good rule in software development (especially packages) is develop only for what is needed, not what you think might be needed. In other words, get it working for whatever version of Python you're running (or is dearest to you) and then take support requests if you want to implement them yourself as people need them.

I have servers that run Python 2.3. :-)

But no, you don't need to support it. Most servers like that are just running, and do not get any new modules installed.

When creating a new module today, 2.6, 2.7, 3.1 and 3.2 is the versions to support. For existing modules you can ask your users. :-)

You should support the latest of the 2.x series (2.7 as of now) and 3.x (3.2 as of now). Unless you have a specific need for supporting older versions, I don't think you need to go there.

As for alternate implementations like IronPython and Jython, you should do that only if needed. It can be time consuming (although perhaps educational) to support you app for all these implementations.

As a side node, to test your app on multiple versions/implementations of Python, I recommend tox.