How to Bootstrap numpy installation in setup.py

Question

I have a project which has a C extension which requires numpy. Ideally, I\'d like whoever downloads my project to just be able to run python setup.py install or

Answer 1

@coldfix's solution doesn't work for Cython-extensions, if Cython isn't pre-installed on the target-machine, as it fails with the error

error: unknown file type '.pyx' (from 'xxxxx/yyyyyy.pyx')

The reason for the failure is the premature import of setuptools.command.build_ext, because when imported, it tries to use Cython's build_ext-functionality:

try:
    # Attempt to use Cython for building extensions, if available
    from Cython.Distutils.build_ext import build_ext as _build_ext
    # Additionally, assert that the compiler module will load
    # also. Ref #1229.
    __import__('Cython.Compiler.Main')
except ImportError:
_build_ext = _du_build_ext

And normally setuptools is successful, because the import happens after setup_requirements are fulfilled. However by importing it already in setup.py, only fall back solution can be used, which doesn't know any about Cython.

One possibility to bootstrap Cython alongside with numpy, would be to postpone the import of setuptools.command.build_ext with help of an indirection/proxy:

# factory function
def my_build_ext(pars):
     # import delayed:
     from setuptools.command.build_ext import build_ext as _build_ext#

     # include_dirs adjusted: 
     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())

    #object returned:
    return build_ext(pars)

...
setup(
    ...
    cmdclass={'build_ext' : my_build_ext},
    ...
)

There are other possibilities, discussed for example in this SO-question.