Currently I have Python 3.1.1 installed on my system, same version on my server with WSGI 3.0 running on Apache 2.2.
I want to keep using Python 3.1, but I'm finding that lots of libraries/frameworks don't support it yet, namely Django, Pylons, MySQLdb, etc.
I also checked an account I have on a friend's server, and it is running Python 2.3.4...
I want to write a sort of blog/forum type application that I can expand into a CMS, and eventually write related desktop applications for, as sort of a long-term pet project.
I'd like to use the newest version of Python possible for best security and highest consistency with the desktop-applications-to-be, while still maintaining a good level of portability, and supporting most of the frameworks and libraries I will use.
But I'm lost on which one I should pick. It seems like 2.4 would have the greatest amount of portability but it's sort of old, and I don't want to wind up using a bunch of post-2.4 features that won't compile, and having to re-write with messier code to compensate for it. 2.6 would be better, but it seems like lots of libraries are still porting over to that, and 3.1 would be the best since it eliminates a lot of cruft from the language.
One thing I'd like to highlight is that it'd be nice to know what I will be missing if I choose an older version of Python. For example, if I were to need my application to run on my old Python 2.3.4 account on my friend's server, what libraries/features would I be lacking that exist in newer versions? What problems would I surely run into that would make me wish I was using Python 2.6 or 3.1? Which of these features would be available via __future__ imports?
So, what would be the best direction to go? Should I just use 2.6 and deal with any issues? Should I go for 2.4 to maximize my ability to possibly distribute it to shared hosting environments? Or should I just jump into 3.1 and have a slightly-crippled application until libraries like MySQLdb catch up?
Begin with Python 2.5 if you're not sure.
Have a look at Google App Engine (based on Django). It's using Python 2.5 and it's free. However, you will not be able to call scipy (for example) or any libraries with "C" inside.
You will have the greatest amount of portability with Python2.5. Moreover, python3k is not really used in the industry.