[takluyver]

Actually, the trend is away from using 2to3 - it's now seen as preferable (and quite possible) to have one codebase which works on both 2 and 3. That's the route Django went for, and what Flask is doing. Numpy also switched from using 2to3 to supporting both from a common codebase.

[randuser]

So restricting yourself to a common subset of Python 2/3 and adding compatibility helpers in your code is the preferred approach now a days?

I'm still not convinced about the whole Python 2 to 3 conversion being worth it (asides from the fact that not porting means your project is seen as not being actively maintained). It has led to added complexity in code so that it works on both versions, increased difficulty in packaging/distribution, having to test/debug on both versions, obsolescencing vast amounts of code that will never be ported, confusion among new users, untold man-hours being spent, ...

I don't mean to be sound so down on Python 3, but it has caused me nothing but additional work and frustration. The supposed benefits of Python 3 are still years away.

[takluyver]

The common subset is most of the language, if you target 2.7 and 3.3. But yes, it has clearly caused extra work. But all the tools I use support Python 3, and I'm looking forward to when new users routinely go for 3.