As far as I know, ShedSkin executables can be compiled as modules and imported in CPython painlessly, so the above is not accurate.
"Shed Skin is an experimental Python-to-C++ compiler designed to speed up the execution of computation-intensive Python programs. It converts programs written in a static subset of Python to C++. The C++ code can be compiled to executable code, which can be run either as a standalone program or as an extension module easily imported and used in a regular Python program."