Add numpy.get_include() argument to setuptools without preinstalled numpy

Question

I am currently developing a python package that uses cython and numpy and I want the package to be installable using the pip install c

Answer 1

One (hacky) suggestion would be using the fact that extension.include_dirs is first requested in build_ext, which is called after the setup dependencies are downloaded.

class MyExt(setuptools.Extension):
    def __init__(self, *args, **kwargs):
        self.__include_dirs = []
        super().__init__(*args, **kwargs)

    @property
    def include_dirs(self):
        import numpy
        return self.__include_dirs + [numpy.get_include()]

    @include_dirs.setter
    def include_dirs(self, dirs):
        self.__include_dirs = dirs


my_c_lib_ext = MyExt(
    name="my_c_lib",
    sources=["my_c_lib/some_file.pyx"]
)

setup(
    ...,
    setup_requires=['cython', 'numpy'],
)

---

Update

Another (less, but I guess still pretty hacky) solution would be overriding build instead of build_ext, since we know that build_ext is a subcommand of build and will always be invoked by build on installation. This way, we don't have to touch build_ext and leave it to Cython. This will also work when invoking build_ext directly (e.g., via python setup.py build_ext to rebuild the extensions inplace while developing) because build_ext ensures all options of build are initialized, and by coincidence, Command.set_undefined_options first ensures the command has finalized (I know, distutils is a mess).

Of course, now we're misusing build - it runs code that belongs to build_ext finalization. However, I'd still probably go with this solution rather than with the first one, ensuring the relevant piece of code is properly documented.

import setuptools
from distutils.command.build import build as build_orig


class build(build_orig):

    def finalize_options(self):
        super().finalize_options()
        # I stole this line from ead's answer:
        __builtins__.__NUMPY_SETUP__ = False
        import numpy
        # or just modify my_c_lib_ext directly here, ext_modules should contain a reference anyway
        extension = next(m for m in self.distribution.ext_modules if m == my_c_lib_ext)
        extension.include_dirs.append(numpy.get_include())


my_c_lib_ext = setuptools.Extension(
    name="my_c_lib",
    sources=["my_c_lib/some_file.pyx"]
)

setuptools.setup(
    ...,
    ext_modules=[my_c_lib_ext],
    cmdclass={'build': build},
    ...
)