If you try to wrap any non-trivial type using SWIG typemaps you will quickly go insane. However to speed up an inner loop you can often get away with a few PyObject* arguments/returns. SWIG will pass those through and you can use the Python/C API directly, e.g. to return a numpy array. Allow SWIG to handle only simple types. The Python/C API is relatively sane, but you'll have to learn the reference counting conventions.
Agreed! On my current project (C++) I found that things get extremely complicated with shared_ptrs and directors. I even ended up contributing some solutions to SWIG.
It all appears to be due to a lack of semantics in the C header. SWIG depends on specifying this stuff in the interface file, but I've often wondered if it wouldn't be better to enhance the C-side, either by standard parameter name conventions or by some Doxygen-like standard comments to indicate ownership and other stuff.
SWIG has this nice potential to generate wrappers for (m)any language(s), but in practice as you said it's often just easier to use the Python API directly instead of trying to make it too general. Shame.
I have a C++ project that is available in multiple languages (Python, Rust, Fortran, Julia and JS), and I decided not to use SWIG partly because of this issue. Instead, I manually maintain a clean C API with everything that I need, and manually wrap this API using whatever is available in other languages. It is a bit more work (and thus incentivize me not to break the API ^^), but allow me to mix and match various ownership semantics throughout the API.
