I would add GIS as a second (if somewhat niche) case. The two big commercial players in the field (ESRI and Safe) as well as most of the open source players all have Python as a scripting language
Also in OpenGEO, looking at their projects, aside from PostGIS it's either Python (and JS) or Java (and JS)
[0] https://docs.djangoproject.com/en/dev/ref/contrib/gis/
They aren't similar. I found Ruby to be really hard to learn: The syntax is a mess, Rails is a nightmare, every Ruby project in existence seems to have a gigantic dependency web consisting of dozens of gems, and the language has a lot of rabid fans (including some HN'ers) who'll become downright hostile to anyone who dares suggest that Ruby's less than perfect...
So if you've survived the clusterf...of the Ruby experience, you may find Python to be a suitable substitute for many projects.
Python has its own set of problems -- the years-long Py3k debacle, super(), and anonymous functions (the latter two of which have been tossed around in this discussion) -- but I've found Python to be a much more positive overall experience than Ruby.