f2py_demo.py calls the Fortran code
f2py requires Fortran Intent()
I have run fairly large complicated Fortran codebases from Python with f2py.
The only modification you have to do to Fortran code to work with f2py is at the subroutine you want to call from Python, add
Intent() for each variable.
If you feel uneasy modifying the source code, you can put a comment like
!f2py Intent(in) :: x
You don’t have to put those comments if you’re modifying the code to add
intent(out), be sure the variable is always initialized for all cases in the subroutine.
Otherwise you may get 0 or an unpredictable result in return (this is true for plain standalone Fortran, too).
f2py currently assumes
intent(in) for all variables, which clearly won’t work for many use cases.
Plain Fortran defaults to
However, with f2py the
intent(inout) will return
None unless the inout variable is a Numpy ndarray.
Scalar inout will be left unmodified.
It’s OK to have the Fortran code expecting a scalar with a 0d ndarray inout.