A lot of stuff powered "by Python" is in practice powered by multi-language infrastructures, which can be pretty complex. For example, the Python ecosystem for data science is mostly implemented under the hood in a mix of C, C++, and Fortran, with high-level Python bindings, due to a mixture of legacy reasons and pure Python being too slow. Obviously lots of people still like the end result, but saying this kind of software is in Python is only half the story.