AttributeError: 'list' object has no attribute 'lower'

[AJ Friend]

I can install my Cython wrapper, https://github.com/ajfriend/scs_python, just fine on OSX with

python setup.py install --cython

(which I'm not entirely sure is best practice, btw).

However, when I try to install the package on Travis-CI or on an Ubuntu virtual machine, I get an error with the traceback

....

  File "/usr/local/lib/python2.7/dist-packages/Cython/Distutils/build_ext.py", line 221, in cython_sources

    (extension.language and extension.language.lower() == 'c++')

AttributeError: 'list' object has no attribute 'lower'

The full traceback can be seen here: https://travis-ci.org/ajfriend/scs_python/jobs/88937838

Any idea what's going wrong and how I can get it working?

Thanks,

AJ

[AJ Friend]

A little more info: 

To try and tease out the error, I run the cython compile step on my OSX machine to produce the appropriate .c extension files. I use that output on a linux machine and run

python setup.py install

which runs without Cython to try and install the package. But I get a very similar error on Linux (which I don't get on OSX):

...

running build_ext

Traceback (most recent call last):

  File "/usr/lib/python2.7/pdb.py", line 1314, in main

    pdb._runscript(mainpyfile)

...

  File "/usr/local/lib/python2.7/dist-packages/setuptools/extension.py", line 45, in _convert_pyx_sources_to_lang

    target_ext = '.cpp' if lang.lower() == 'c++' else '.c'

AttributeError: 'list' object has no attribute 'lower'

Uncaught exception. Entering post mortem debugging

Running 'cont' or 'step' will restart the program

> /usr/local/lib/python2.7/dist-packages/setuptools/extension.py(45)_convert_pyx_sources_to_lang()

-> target_ext = '.cpp' if lang.lower() == 'c++' else '.c'

(Pdb) p lang

['f', '7', '7', 'f', '7', '7']

Running the setup.py script under Pdb suggests that the variable `lang` should be a string instead of a list, so I'm not sure why that's happening. I'm also not sure if its reasonable that Fortran

is in the conversation, since my module is in C (although it does use blas and lapack).

Could this possibly be a Cython bug? More likely, I'm doing something wrong, but any help tracking it down would be appreciated.

Thanks,

AJ

[AJ Friend]

Ah, I figured out what I was doing wrong.

I was building up a dictionary of keyword arguments to instantiate the Extension modules, and part of that included appending the output of numpy.distutils.system_info.get_info

for the blas/lapack info. Almost all of the keys match up correctly (define_macros, library_dirs, ...), except the 'language' key, which is exactly what was causing my error.

Sorry to debug out loud! :)

AJ