How to Bootstrap numpy installation in setup.py

The following works at least with numpy1.8 and python{2.6,2.7,3.3}:

from setuptools import setup
from setuptools.command.build_ext import build_ext as _build_ext

class build_ext(_build_ext):
    def finalize_options(self):
        _build_ext.finalize_options(self)
        # Prevent numpy from thinking it is still in its setup process:
        __builtins__.__NUMPY_SETUP__ = False
        import numpy
        self.include_dirs.append(numpy.get_include())

setup(
    ...
    cmdclass={'build_ext':build_ext},
    setup_requires=['numpy'],
    ...
)

For a small explanation, see why it fails without the “hack”, see this answer.

Note, that using setup_requires has a subtle downside: numpy will not only be compiled before building extensions, but also when doing python setup.py --help, for example. To avoid this, you could check for command line options, like suggested in https://github.com/scipy/scipy/blob/master/setup.py#L205, but on the other hand I don’t really think it’s worth the effort.