[51109]

It is good advice, because it works. You can give reasonable explanations for Python 3, involving politics, the future, and dead languages, while still having your students be confused when Google releases TensorFlow with only 2.7 support. Hard language is his style. He loathes anything that gets in the way of being a productive programmer. See: http://programming-motherfucker.com/

[hoodoof]

So in general I should never move to a new software technology until all software with the old no longer exists?

[51109]

You should do whatever makes you happy and productive. So install 2.7 and ignore the people who say 3 is the future (unless you can work better in 3).

[hoodoof]

Hang on, the advice given is not "do whatever makes you happy and productive.", the advice given is "never use Python 3 until every line of Python code on your computer is written with Python 3".

And please explain why to ignore people who say Python 3 is the future, I don't understand why.

[51109]

I thought you were asking me a (loaded) question. The advice given was not "never use Python 3 until...", that was a suggested reply to people telling newcomers to go for Python 3. Perhaps too tongue-in-cheek, but coming from someone who taught millions of people Python, worth noting.

You ignore people who say that Python 3 is the future, because it will make you happy and more productive when you can run modern libraries that have a 2.7 requirement. Or you don't ignore them, and get into endless debates about how almost all libraries support 3, and that you need to spend just 1 in 20 days of your time worrying about getting your code to work, instead of... programming. But if that makes you happy, you should do that.