As a reasonable proficient Python programmer, I'm wondering what a good second language to learn would be. More specifically, something that does well the things that Python doesn't in general do as well. My first guess would be C/C++ since it's got easy extensibility with Python and because it offers generally better performance, but I'm wondering if Java or C# might be a better or at least equivalently good option with different up/downsides compared to C/C++.