> operating system releases younger than 2013ish This seems like it depends on what kinds of OS you regularly use. On Linux the deployment situation isn't quit

> operating system releases younger than 2013ish This seems like it depends on what kinds of OS you regularly use. On Linux the deployment situation isn't quite that dire. Python3 has been in Debian stable since Debian 6 (aka Squeeze, released February 2011), so running Python3 code isn't a problem if the machine is even close to up to date. On Ubuntu the situation is even reversed: Python3 is default, and starting in 2014 it will be the only supported version, with Python2 support being dropped. It will still be installable out of "universe", but the goal is to drop Python2 from "main" by the release of 14.04 LTS in 2014, because LTS releases promise 5 years of support, and they don't want to be supporting Python2 into 2019.