Specify cython output file

Question

It seems that by default setup from distutils.core with cmdclass set to build_ext, compiles a cpp or c file in the current working directory. Is there a way to determine where the generated c code is written to? Otherwise, a repository will be littered with generated code.

For example this file setup.py will write a file example.c to the current working directory:

from distutils.core import setup
from Cython.Build import cythonize

setup(
      ext_modules = cythonize("example.pyx"))

Answer 1

after initializing an Extension, the parameters can be set to create c in temp directory.

 module  = Extension("temp", "temp.pyx")
 module.cython_c_in_temp = True 

Answer 2

Your setup.py is fine.

To get it to build to a different location, invoke python in the following way:

python setup.py build_ext --build-lib <build directory>

I use the following make rules to automate this:

python_lib_dir=src/lib

cython_output = $(patsubst $(python_lib_dir)/%.pyx,$(python_lib_dir)/%.so, $(shell find $(python_lib_dir) -name '*.pyx'))

$(cython_output):%.so:%.pyx      
    python setup.py build_ext --build-lib $(python_lib_dir)

Answer 3

You can pass the option build_dir="directory name" to Cythonize

# rest of file as before
setup(
      ext_modules = cythonize("example.pyx",
                              build_dir="build"))

The above code will put the generated c files in the directory "build" (which makes sense, since by default it's where distutils puts temporary object files and so forth when it's building).

---

My original answer had working, not build_dir. Thanks to @ArthurTacca for pointing out that that no longer seems to be right.