Also, a lot of research on dynamic languages is being done with Ruby, e.g. TruffleRuby, JRuby, RubyOMR, and probably a few more I'm forgetting. Each of those projects is an impressive body of work in and of itself that points to Ruby being very alive and well. Oh, almost forgot about MRuby. I don't think there are similar efforts for Python. In some sense Python is much more stagnant these days in terms of innovation at the language level.