Python modules - how to create & which are better

[grbgooglefan]

I have embedded Python in my C++ application & creating Python
function from the expression. I am then evaluating those Python
compiled function (byte code) using PyObject_CallObject.

I want to create a Python module which will have functions called by
my user defined functions from the embedded Python interpreter.

What will be best approach in this case? Should I be creating
normal .py modules or .so modules (python extended with C code)?
For me, most important is the executiong speed of the code in these
modules. I want them to be fast, as those will be executed lot many
times & in time bound fashion.

Any suggestions on this?