[lmitchell]

I don't even think it's about pretty code - I think it's more related to what one sibling of the post you replied to mentioned, which is that there are tons of communities (among them machine learning, but including tons of stats-heavy academic programming) which would REALLY like to do some extremely heavy work in Python, not because it's necessarily the best, but because it's what they know. Academics in particular (not CS academics, but stats and experimental sciences people) can be forgiven for wanting to stick with Python - they aren't programmers, they don't want to waste time learning programming language skills that are largely irrelevant to their job. All they want is to pick up an easy language and be able to do their work in it, but once their work gets heavy, the language starts to fight them. And that's a really popular use case for Python, I think.