[dvirsky]

Most of this stuff is great and I'm actually looking forward to moving to py3k. But I've been looking forward for a few years now, though, and it seems like that will continue to for a while longer.

The main problem for me remains dependencies. Python makes it so easy to integrate stuff via pip/easy_install, but that's a double edged sword in this case: Since there's such a huge abundance of great libraries for anything out there, and they're so easy to install - people use them. And now I'm stuck with non py3k compliant libs in a big codebase (some of them not trivial), and suddenly there is a much bigger cost to switching - migrating away from, or porting of all those deps.

So now all those up-sides which are nice to have but are not real game changers (I'm handling Unicode fine - albeit in an clunky and ugly way, but it works), are not worth the pain. And that's sort of a chicken-and-egg thing.

If there was a much bigger gain from switching, that will outweigh the cost - e.g. better concurrency, better overall performance - it would be worth the pain. Otherwise, I guess I might use py3k for new stacks I'll build from scratch, but not for the current stack I work with.

[aidos]

Do you have a list of dependencies that are causing you the issues? When I did my migration (about 9 months ago) I found that there were a few dependencies that had been superseded by much better libraries. At the time there were a couple where I had to use a py3 branch, but no longer.

[dvirsky]

One of the most annoying ones is Thrift. But I just googled it and it seems like they are very close to supporting Python 3. A couple others - mysql-python, fabric, oauth2. These are the ones that are on the wall-of-shame. But I didn't test the entire dependency set.

[aidos]

I think on the mysql front there are a few alternatives (I use postgres now - and if there was any way of going that route, I'd do that instead). I believe the pure python version is the popular choice these days [0].

I mentioned it because when I went through the process, I was looking for py3 support from my existing libraries and didn't consider swapping them out (as in, initially it didn't even occur to me).

In some cases I found far better libs that were more actively developed (eg I ended up using xlsxwriter for my excel stuff and it was way better than my previous solution).

[0] https://pypi.python.org/pypi/PyMySQL

ps I believe they like to call it "Wall of Superpowers" these days :)

[tenfingers]

Depends on your requirements on code/performance, but in one of my projects I've been gradually switching over to python 3 (actually, moving old stuff over from 2) by using this module:

https://pypi.python.org/pypi/python-bond

It spawns a second python process that you can call/execute code from almost invisibly, first-class exceptions included. The main difference with other similar solutions is that it support call backs: a remote function can call back new code, and can do it so recursively.

You can intertwine old code and new one.

The main drawback is that it's not efficient for small/lightweight functions.