fatal error: Python.h: No such file or directory

[mbdevpl]

file testing.py contains the following:

print('hello world')

when compiling using cythonize the compilation succeeds:

$ cythonize -i testing.py 
running build_ext
building 'testing' extension
creating /tmp/cython_tests/tmprxz7ue8g/tmp
creating /tmp/cython_tests/tmprxz7ue8g/tmp/cython_tests
gcc -pthread -Wno-unused-result -Wsign-compare -Wunreachable-code -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -fPIC -I/home/user/.local/include/python3.5m -c /tmp/cython_tests/testing.c -o /tmp/cython_tests/tmprxz7ue8g/tmp/cython_tests/testing.o
gcc -pthread -shared /tmp/cython_tests/tmprxz7ue8g/tmp/cython_tests/testing.o -o /tmp/cython_tests/testing.cpython-35m-x86_64-linux-gnu.so

(also the compiled extension runs ok and hello world is printed)

but when using cytherize.py, there is a build error:

$ python3.5 ~/.local/bin/cytherize.py testing.py
cython -a -p -o /tmp/cython_tests/__cythercache__/testing.c /tmp/cython_tests/testing.py
gcc -fPIC -shared -w -O3 -I/home/user/.local/include/python3.5m-I/home/user/.local/include -L/home/user/.local/lib -o /tmp/cython_tests/testing.so /tmp/cython_tests/__cythercache__/testing.c -lpython3.5m
/tmp/cython_tests/__cythercache__/testing.c:4:20: fatal error: Python.h: No such file or directory
compilation terminated.
Error in source file, see above

It seems Cython is using different flags to compile the extension than Cyther, and at least in my case the Cython flags seem to result in working binary, but not Cyther flags...

Am I supposed to add all the missing flags manually, or is this some to-be-resolved issue with Cyther?

[nickpandolfi]

Ok, I finally got around to attempting to fix this issue. This is definitely an issue to be resolved soon. Cyther is supposed to do it all for you. The problem for me is obtaining all of these platform / operating system dependent flags. I've tried many, many, many times to do this through distutils.ccompiler.CCompiler as well as its sub-classes, but the resulting mess is just simply nasty. Cython seems to be doing it internally (that is, figuring out the different flags necessary), and then just pass them to gcc. I don't even know where to start looking for where the flags are generated...

Thank you very much for the report though! It was very helpful,
Nick

[nickpandolfi]

I have successfully replicated the issue on a local Xubuntu installation. I'm very close to a fix!