Pass numpy's include dir to Cmake from Setuptools

Question

I have a C++ library which I have successfully exposed to python using Pybind11.

In the CmakeLists.txt file, I have added the numpy include like this:

include_directories("C:\\Python37\\Lib\\site-packages\\numpy\\core\\include")

This works, but is undesirable. I would like to pass the numpy include directory from my setup.py file.

My setup.py file looks very much like this one:

import os
import re
import sys
import sysconfig
import platform
import subprocess

from distutils.version import LooseVersion
from setuptools import setup, Extension
from setuptools.command.build_ext import build_ext


class CMakeExtension(Extension):
    def __init__(self, name, sourcedir=''):
        Extension.__init__(self, name, sources=[])
        self.sourcedir = os.path.abspath(sourcedir)


class CMakeBuild(build_ext):
    def run(self):
        try:
            out = subprocess.check_output(['cmake', '--version'])
        except OSError:
            raise RuntimeError(
                "CMake must be installed to build the following extensions: " +
                ", ".join(e.name for e in self.extensions))

        if platform.system() == "Windows":
            cmake_version = LooseVersion(re.search(r'version\s*([\d.]+)',
                                         out.decode()).group(1))
            if cmake_version < '3.1.0':
                raise RuntimeError("CMake >= 3.1.0 is required on Windows")

        for ext in self.extensions:
            self.build_extension(ext)

    def build_extension(self, ext):
        extdir = os.path.abspath(
            os.path.dirname(self.get_ext_fullpath(ext.name)))
        cmake_args = ['-DCMAKE_LIBRARY_OUTPUT_DIRECTORY=' + extdir,
                      '-DPYTHON_EXECUTABLE=' + sys.executable]

        cfg = 'Debug' if self.debug else 'Release'
        build_args = ['--config', cfg]

        if platform.system() == "Windows":
            cmake_args += ['-DCMAKE_LIBRARY_OUTPUT_DIRECTORY_{}={}'.format(
                cfg.upper(),
                extdir)]
            if sys.maxsize > 2**32:
                cmake_args += ['-A', 'x64']
            build_args += ['--', '/m']
        else:
            cmake_args += ['-DCMAKE_BUILD_TYPE=' + cfg]
            build_args += ['--', '-j2']

        env = os.environ.copy()
        env['CXXFLAGS'] = '{} -DVERSION_INFO=\\"{}\\"'.format(
            env.get('CXXFLAGS', ''),
            self.distribution.get_version())
        if not os.path.exists(self.build_temp):
            os.makedirs(self.build_temp)
        subprocess.check_call(['cmake', ext.sourcedir] + cmake_args,
                              cwd=self.build_temp, env=env)
        subprocess.check_call(['cmake', '--build', '.'] + build_args,
                              cwd=self.build_temp)
        print()  # Add an empty line for cleaner output

setup(
    name='python_cpp_example',
    version='0.1',
    author='Benjamin Jack',
    author_email='[email protected]',
    description='A hybrid Python/C++ test project',
    long_description='',
    # add extension module
    ext_modules=[CMakeExtension('python_cpp_example')],
    # add custom build_ext command
    cmdclass=dict(build_ext=CMakeBuild),
    zip_safe=False,
)

After having a look at some SO questions like this, I know that you can get the numpy include directory with numpy.get_include().

However, adding the include directory to the path inside the function build_extension with this line ext.include_dirs.append(numpy.get_include()) seems to have no effect.

I'd like to know how to pass the include directory properly.

Answer 1

Is your cmake build using the wrong numpy path or not finding numpy at all? If it's the wrong path, you could try prepending instead of appending numpy.get_include():

ext.include_dirs.insert(0,numpy.get_include())