Very limited shared state (only c types, including structs), which in practice means (for non trivial apps) some form of marshaling from python classes to the C

Very limited shared state (only c types, including structs), which in practice means (for non trivial apps) some form of marshaling from python classes to the C structs. Boilerplate abound! In other words, nothing behind mmap with simple size calculations, which is what you'd really want to abstract away.