Whilst the design of Ruby is far superior, Python has a wider range of data structures which may explain why it managed to gain a foothold in the scientific world. Both are multi-paradigm languages but procedural Python is also a little more idiomatic than its equivalent in Ruby which maybe makes Python easier for scientists who don't want to go all-in learning a more elegant language. Pretty soon in Python's rise it became all about libraries. Ruby never took the scientific world that seriously until it was too late.