Change Cython's naming rules for .so files

Question

I\'m using Cython to generate a shared object out of Python module. The compilation output is written to build/lib.linux-x86_64-3.5//.cpyt

Answer 1

This behavior has been defined in distutils package. distutils uses sysconfig and "EXT_SUFFIX" config variable:

# Lib\distutils\command\build_ext.py

def get_ext_filename(self, ext_name):
    r"""Convert the name of an extension (eg. "foo.bar") into the name
    of the file from which it will be loaded (eg. "foo/bar.so", or
    "foo\bar.pyd").
    """
    from distutils.sysconfig import get_config_var
    ext_path = ext_name.split('.')
    ext_suffix = get_config_var('EXT_SUFFIX')
    return os.path.join(*ext_path) + ext_suffix

Starting with Python 3.5 "EXT_SUFFIX" variable contains platform information, for example ".cp35-win_amd64".

I have written the following function:

def get_ext_filename_without_platform_suffix(filename):
    name, ext = os.path.splitext(filename)
    ext_suffix = sysconfig.get_config_var('EXT_SUFFIX')

    if ext_suffix == ext:
        return filename

    ext_suffix = ext_suffix.replace(ext, '')
    idx = name.find(ext_suffix)

    if idx == -1:
        return filename
    else:
        return name[:idx] + ext

And custom build_ext command:

from Cython.Distutils import build_ext

class BuildExtWithoutPlatformSuffix(build_ext):
    def get_ext_filename(self, ext_name):
        filename = super().get_ext_filename(ext_name)
        return get_ext_filename_without_platform_suffix(filename)

Usage:

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