I've never touched Python myself, but I've noticed it has a loyal following. Can't go wrong with C++ if you want that solid base though.
Pretty much all devices and Os have a c++ compiler, so you'd be able to code for anything and everything. It's hard, but it's really the master programming language from which all others are dummied down versions. Either way if you'd want my recommendation, I'd pick either: C++ (hard) or Java (easy).
If you dive into Python, let me know how it is.