And then lots of things were built on top of Numpy - image processing, reading GIS raster data, scipy, pandas, etc etc - and they're all trivial to combine because it's all just Numpy arrays.
Python also had a very friendly and approachable community from the start, and great docs, while Ruby had its documentation in Japanese only for some time.
Django is also top quality, imo. Similar to Rails. But it always seemed Ruby was only good for Rails, whereas Python combines with everything.
So as usual, it's not about the language, it's about the rest.