f2py with include files

Question

I am compiling a fortran program called prog.f. It contains an include file called test.inc. This below runs successfully and shows that my include file is found. I have a prog.so file generated.

f2py -c prog.f -m prog

However when I call this module from python I get this error message:

Python 2.7.3 (default, Aug  1 2012, 05:14:39) 
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import prog
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: ./prog.so: undefined symbol: unknown_function_

I suspect something to do with my compilation arguments but I am not too familiar with Fortran. Do I need to include my include file as well? If so how?

Answer 1

Yes, you need the include file. It might be something as simple as:

f2py -c include_file.f prog.f -m prog

although I haven't tested that. Alternatively, you might need to use the fortran include statement to include include_file into prog ... Also, if you're more familiar with C, virtually all fortran compilers that I know use the convention that prog.F is fortran code that should be preprocessed by cpp . So you could probably get your file included that way as well.

Answer 2

I also ran into this problem, and was able to find other discussions that simply stated that current f2py does not support preprocessing of files, such as #include statements and conditional compilation. https://groups.google.com/forum/#!topic/f2py-dev/aW65sEoSdG8

http://mail.scipy.org/pipermail/numpy-discussion/2009-November/046381.html

Two solutions: Simplest: If you are using gfortran to compile your code, rename any .f90 or .f file to .F90 or .F. Using a capital letter keys gfortran to automatically use the preprocessor (even if you don't specify).

Second: Use your Fortran compiler to preprocess the file and save the result as an intermediate Fortran code to be sent to f2py.

gfortran -E -D<Defines-for-compiler> file.f -cpp  -o outdir/file.f

where -E is the command to tell gfortran to just preprocess the file (may vary from compiler to compiler), and -D option to define any values to use during the preprocessing.

Saving the file to another directory (or changing the name completely) is necessary to avoid overwriting the original .f file.