Some practice and demo about python c extension via python api, also some general notes.

• Python header files
  • Python.h
    • Incording to Python document, this header preprocess alot of things (such as stdlib.h, stdio.h), so you shuould always include it first before any other staderd header file.
    • #define PY_SSIZE_T_CLEAN
• Method functions
  • The file then definds the function to be called in Python, use two python object as input, then returns a python object back to interpreter as result, or return a NULL to trigger an exception(Note: return a NULL didn't handle an error).
  • Incording to Python Programming by Mark Lutz

    you shuould use more specific type names, but don't always have to, because Python calls them by pointer, not name.

• Registration table
  • The Python.h file provides an initalized table (e.g PyMethodDef, PyModuleDef)that maps function attribute to function pointers(address)
• Initialzation funciton
  • Finally, the Python.h provide a initialzation function, witch Python call the fist time when this module is imported into a python Program. When Py_Init_module is called, the function will bulid a dict table in the current module.Once so initialized, calls from Python are routed through registration table's function table.