setup_requires with Cython?
Starting from 18.0 release of setuptools
(released on 2015-06-23) it is possible to specify Cython
in setup_requires
and pass *.pyx
modules sources for regular setuptools.Extension
:
from setuptools import setup, Extensionsetup( # ... setup_requires=[ # Setuptools 18.0 properly handles Cython extensions. 'setuptools>=18.0', 'cython', ], ext_modules=[ Extension( 'mylib', sources=['src/mylib.pyx'], ), ],)
You must wrap the from Cython.Build import cythonize
in a try-except
, and in the except
, define cythonize
as a dummy function. This way the script can be loaded without failing with an ImportError
.
Then later when the setup_requires
argument is handled, Cython
will be installed and the setup script will be re-executed. Since at that point Cython
is installed, you'll be able to successfully import cythonize
try: from Cython.Build import cythonizeexcept ImportError: def cythonize(*args, **kwargs): from Cython.Build import cythonize return cythonize(*args, **kwargs)
EDIT
As noted in comments, after setuptools deals with missing dependencies, it won't re-load Cython. I hadn't thought of it before, but you could also try a late-binding approach to stubbing out cythonize
There seems to be a third way of having build dependencies installed before executing the actual setup.py
described here (requires pip
):
https://cython.readthedocs.io/en/latest/src/userguide/source_files_and_compilation.html#basic-setup-
In essence:
- Create the file
pyproject.toml
with the following contents:
[build-system]requires = ["setuptools", "wheel", "Cython"]
- Use
pip install -e .
for setting things up