How to check the version of the python API at compile time from a C extension module?

Yes, patchlevel.h in the Python include dir defines what you are looking for:

#define PY_MAJOR_VERSION    2
#define PY_MINOR_VERSION    5
#define PY_MICRO_VERSION    2

I think what you need is PY_VERSION_HEX

there is one line in c code generated by cython

PY_VERSION_HEX < 0x02040000

#ifndef Py_PYTHON_H
  #error Python headers needed to compile C extensions, please install development version of Python.
#elif PY_VERSION_HEX < 0x02040000
  #error Cython requires Python 2.4+.
#else