M.-A. Lemburg schrieb am 07.09.2018 um 11:02:
Cython allows you to wrap existing C code, but if you want to use Python objects in C or details which are not exposed at the Python level, you still need the Python C API to work with those.
Well, you can use the C-API, because Cython allows you to call arbitrary C code. But that doesn't mean you should. In fact, the code that Cython generates is usually faster than the "obvious" C-API functions, so not using the C-API explicitly in Cython has many advantages, such as not relying on CPython version details, simplifying your code, and speeding it up.
And Cython is not just a tool to "wrap existing C code". That's only one of its major use cases. Speeding up Python code, and writing C code without writing C code, are just as important.