[nickdavidhaynes]

Jupyter and matplotlib aren't designed to actually do any calculation (they are just for communicating results) so it doesn't make sense for them to be written in C. Pandas has a ton of pure Python code, but if you dig through the layers of abstraction, all of the core algorithms are implemented in cython or make calls to numpy (which is calling C code).

Bottom line, when you're using an established Python scientific computing library to do numerical calculations, you're calling C (or maybe Fortran) routines.