I do a lot of scientific computing in Python and have had awful experiences with Python 3. We encourage everyone who comes into our lab to work with 2.7 because the libraries are all there. It's true that Numpy and Scipy now build for Python 3, but another key library, PIL, is lost in limbo with no clear timeline for porting last I checked.
The only reason I've used Python 3 at all was because of project involving blender. I needed to do in-memory JPEG compression for quickly streaming images from the game engine. In Python 2, this is a couple lines of code using PIL. Instead, I ended up having to write my own pyjpeg module that provided a ctypes interface to a custom libjpeg-based compression library. I'm proud of the result, but the aggravation and frustration that entailed has removed any desire I have to move to Python 3.
I don't see why the irresponsible maintainership of PIL should reflect badly on Python 3. Pillow is a fork of PIL which was created to address some of these problems:
I should clarify that Python 3, by itself, is fine. I had the unfortunate situation of having to use it for a task in which no suitable library existed, which led to a significant amount of unwelcome additional effort.
However, until those library deficiencies are fully met, it makes no sense to move forward from 2.7.
Thanks for the Pillow link, btw. I was unaware of it.
The only reason I've used Python 3 at all was because of project involving blender. I needed to do in-memory JPEG compression for quickly streaming images from the game engine. In Python 2, this is a couple lines of code using PIL. Instead, I ended up having to write my own pyjpeg module that provided a ctypes interface to a custom libjpeg-based compression library. I'm proud of the result, but the aggravation and frustration that entailed has removed any desire I have to move to Python 3.