pywafo/wafo/source/test_f90/hello.txt

[f2py] Confused with fortran 90 modules

Dede ded.espaze at laposte.net 
Fri Oct 19 11:45:36 EEST 2007
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Hi Peter,

I had recently the same problem with the program of a friend. He
had done a similar work but he was using reals. We succeeded to make
it work by using only "real(kind=8)" on the Python side, that's why I
have introduced a new file: hello_interface.f90. To reuse the Fortran
subroutines, we wrote a conversion function, so I have changed a
little types.f90. My files:

types.f90
!--------------------------!
      module types
        integer, parameter :: WP=4, intdim=selected_int_kind(8)
      contains
        function to_intdim(int_value)
            integer(kind=8) :: int_value
            integer(intdim) :: to_intdim
            to_intdim = int_value
        end function to_intdim
      end module types
!--------------------------!

hello.f90
!--------------------------!	
	module hello
        use types
        contains
            subroutine foo(a)
              integer(intdim) :: a
              print*, "Hello from Fortran!"
              print*, "a=",a
            end subroutine foo
        end module hello
!--------------------------!  

hello_interface.f90
!--------------------------!
      module bindings
      use types
      use hello
      contains
        subroutine pyfoo(a)
            integer(kind=8) :: a
            call foo(to_intdim(a))
        end subroutine pyfoo
      end module bindings
!--------------------------!

For using the Fortran modules in Python, the code needs to be compiled
with dynamic flags, so -fPIC is introduced:

gfortran -fPIC -c types.f90
gfortran -fPIC -c hello.f90

The Python module needs to include the generated objects:

f2py -m hello -c types.o hello.o hello_interface.f90 

f2py -m hello -c types.o hello.o hello_interface.f90 --fcompiler=gnu95 --compiler=mingw32 -lmsvcr71

Now you should have the module "hello.so", and I hope you will get in 
a python session:

# ipython
.
.
In [1]: import hello

In [2]: hello.bindings.pyfoo(4)
 Hello from Fortran!
 a=           4

Thanks to Python, it is then easy to write a module that hide the f2py
interface, so then by doing:

import hello
hello.foo(4)

you directly get the work done.

Cheers,

Dede


On Thu, 18 Oct 2007 01:08:07 -0600
"Peter Schmitt" <pschmittml at gmail.com> wrote:

> I'm fairly new to Fortran, and I'm just starting out with f2py... I
> have a question which is best illustrated by example:
> 
> In fortran, I have a program that calls a module, such as:
> 
> hello.f90:
> ! -----------------------------------------!
> program hello
>   use types
> 
>   call foo(5)
> 
>   contains
>   subroutine foo (a)
>     integer(intdim) :: a
>     print*, "Hello from Fortran!"
>     print*, "a=",a
>   end subroutine foo
> 
> end program hello
> ! -----------------------------------------!
> 
> types.f90
> ! -----------------------------------------!
> module types
>   integer, parameter :: WP=4, intdim=selected_int_kind(8)
> end module types
> ! -----------------------------------------!
> 
> To build this program in plain old fortran, I issue the following
> three commands to compile and link:
> gfortran -c types.f90
> gfortran -c hello.f90
> gfortran types.o hello.o -o HELLO
> 
> 
> Now if I want to call "foo(5)" in Python using f2py, I change
> hello.f90 as follows:
> 
> hello.f90:
> ! -----------------------------------------!
> use types
> 
> subroutine foo (a)
>   integer(intdim) :: a
>   print*, "Hello from Fortran!"
>   print*, "a=",a
> end subroutine foo
> ! -----------------------------------------!
> 
> Then compile types and hello
> f2py2.5 --fcompiler=gfortran -c -m types types.f90
> f2py2.5 --fcompiler=gfortran -c -m hello hello.f90
> 
> but I can't compile hello.f90.  I get the following error:
> 
> > Traceback (most recent call last):
> >   File
> > "/home/pschmitt/usr/local/lib/python2.5/site-packages/numpy/__init__.py",
> > line 31, in <module>
> >     from _import_tools import PackageLoader
> >   File
> > "/home/pschmitt/usr/local/lib/python2.5/site-packages/numpy/_import_tools.py",
> > line 5, in <module>
> >     from glob import glob
> >   File "/usr/lib/python2.5/glob.py", line 4, in <module>
> >     import fnmatch
> >   File "/usr/lib/python2.5/fnmatch.py", line 13, in <module>
> >     import re
> >   File "/usr/lib/python2.5/re.py", line 276, in <module>
> >     copy_reg.pickle(_pattern_type, _pickle, _compile)
> > AttributeError: 'module' object has no attribute 'pickle'
> > 'import site' failed; use -v for traceback
> > Traceback (most recent call last):
> >   File "/home/pschmitt/usr/local/bin/f2py2.5", line 3, in <module>
> >     import os, sys
> >   File "/usr/lib/python2.5/os.py", line 696, in <module>
> >     import copy_reg as _copy_reg
> >   File "/usr/lib/python2.5/copy_reg.py", line 7, in <module>
> >     from types import ClassType as _ClassType
> > ImportError: cannot import name ClassType
> >
> 
> I'm having a hard time wrapping my head around f2py and f90
> modules... can someone offer any help?
> 
> Thanks!
> -Pete

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