Cython conditional compilation based on external value given via `setuptools`

Question

I try to conditionally generate C code from a Cython pyx file. I found in the Cython documentation that I can use DEF to define a value and IF to conditionally generate code based on a defined value, but how can I set the value from the setup.py via Extension from setuptools.

Thank You

Answer 1

Thank you for the link.

The interesting flag in the setup.py is cython_compile_time_env. And to import the Extension from Cython.

from setuptools import setup
from Cython.Distutils.extension import Extension

ext = Extension(
    name,
    include_dirs=include_dirs,
    cython_compile_time_env=dict(OPENMP=True),
    sources=['test.pyx'])

setup(name=name,
      cmdclass=dict(build_ext=build_ext),
      ext_modules=[ext])

And in the test.pyx:

...
IF OPENMP:
#Do openmp
ELSE:
#No openmp
...

Cython conditional statements (IF...ELSE above) are documented here.