@aegilops For a while #IronPython appeared to be "stuck" in 2.7 just like #Jython, but in December they released version 3.4 and they've ported f-strings from #CPython 3.6.
I cannot imagine what goes into implementing Python in other programming languages, and for that they deserve my admiration. But it is indeed a shame Jython has not moved past 2.7 in almost eight years.
Maybe Inductive Automation will open their platform to other scripting languages, but until then I'm stuck in 2.7 too.