One of the companies where I teach just (in 2016) upgraded one of their core systems to Python 2.7. That's after years in which it was written in Python 2.4.

One of the companies where I teach just (in 2016) upgraded one of their core systems to Python 2.7. That's after years in which it was written in Python 2.4. Yes, 2.4, the same version my great-grandparents ran back in the Old Country. So yes, things are rewritten. And things are upgraded. But at a glacier's pace. 2020 is coming soon -- in about three years. There's no way that companies will upgrade some of these systems to Python 3 during that time. Some things, sure -- but there's a lot of legacy code out there, and I don't see them spending the time and money to upgrade something that already works.