Python would be the most popular option, but, for an OO language, Ruby feels clean and intuitive to me in a way that other languages, especially Python, don't.

Python would be the most popular option, but, for an OO language, Ruby feels clean and intuitive to me in a way that other languages, especially Python, don't. It has a performance cost, though. The two languages' performance may be roughly equivalent, but Python has more native-code libraries for performance-critical tasks. You don't see many ML projects in Ruby. :) There's crystal-lang, but that has a much smaller community behind it. Julia, though, if you're looking for a language that isn't OO in addition to functional.