[lmm]

It is very useful for a beginner to start with python3, as python3 makes the difference between strings and byte sequences much clearer.

The majority of python code on my computer is now python 3.

[teach]

If you're worried about the distinction between strings and byte sequences, you're thinking about a different sort of "beginner".

[lmm]

A beginner will want to read and write files pretty early on. In Python 2 it's very easy to e.g. ignore that you need to pass the 'b' option for reading binary files and write scripts that seem to work, and then silently corrupt data when run on windows. Which is not a good experience.