This is sadly true, although as Lennart's guide makes it clear many of those can trivially be updated to run on both. I'm hoping the next year leads to a lot of the simple updates happening so tutorial code can run against both — with `from __future__ import absolute_import, division, print_function, unicode_literals` quite a few programs can easily be single-source using only stock Python 2.7 / 3.4 without needing to introduce something like six.