Notes on f2py and cython

• f2py takes source Fortran code and compiles it to a Python-readable module.
• Cython takes Python code and compiles it to C, which means the module will run faster.

Compiling Fortran code

Fortran code is compiled into a Python-readable .pyd file using the package f2py. This can be done either from the command line, e.g.

f2py -c -m helloworld_fortran helloworld_fortran.f90

or from within a Python file using f2py2e. We use the former option in this repo.

To check that you can compile and load fortran modules, you will compile the simple helloworld_fortran.f90 module included in this repo. The module has a single subroutine called fortran_greetings that will be turned into a Python function.

Cythonizing Python code

This procedure takes Python code and turns it into a compiled .pyd module, which means it is potentially much faster.

You can cythonize either in your setup.py file or from the command line. We’ll use the latter, because we had trouble getting the inplace flag to work, which meant that the .pyd files were in the wrong place.

The terminal command to cythonize code (assuming you have Cython installed and correctly configured compilers) is

cythonize -a -i helloworld_cython.pyx

To check that you can cythonize python code, you will compile the helloworld_cython.pyx module included in this repo. The module has a single subroutine called cython_greetings that will be turned into a Python function.