Using Fortran libraries from Python?

[Carl]

I have experimented with f2c and swig-generated wrappers to create python
modules from Fortran files.

I think I'm missing something when I'm building the Python module, because
when I import the built module the Python interpreter returns the
following:

import LDSsobol

Traceback (most recent call last):
File "<stdin>", line 1, in ?
File "LDSsobol.py", line 4, in ?
import _LDSsobol
ImportError: /usr/lib/libf2c.so.0: undefined symbol: MAIN__

This is how I built LDSsobol:
gcc -c LDSsobol.c
gcc -c LDSsobol_wrap.c -I/usr/include/python
gcc -shared LDSsobol.o LDSsobol_wrap.o -l f2c -o _LDSsobol.so

Any help is appreciated!

Carl

[Skip Montanaro]

Carl> I have experimented with f2c and swig-generated wrappers to create
Carl> python modules from Fortran files.

...

Carl> Any help is appreciated!

I'd take a look at f2py, part of the scipy package (and also available on
its own):

http://www.scipy.org/
http://www.python.org/pypi?%3Aaction..._pypi_hidden=0

Skip

[Berthold Höllmann]

Carl <ph***********@chello.se> writes:

I have experimented with f2c and swig-generated wrappers to create python
modules from Fortran files.

I think I'm missing something when I'm building the Python module, because
when I import the built module the Python interpreter returns the
following:

import LDSsobol

Traceback (most recent call last):
File "<stdin>", line 1, in ?
File "LDSsobol.py", line 4, in ?
import _LDSsobol
ImportError: /usr/lib/libf2c.so.0: undefined symbol: MAIN__

This is how I built LDSsobol:

gcc -c LDSsobol.c
gcc -c LDSsobol_wrap.c -I/usr/include/python
gcc -shared LDSsobol.o LDSsobol_wrap.o -l f2c -o _LDSsobol.so

Hello Carl,

Googleing for "libf2c.so.0: undefined symbol: MAIN__" I found only 8
hits, some links broken, but also

<http://www.physics.orst.edu/~bertrand/slatec/jnislatec/JNI_Slatec.html>

where I found:

Currently users of f2c will probably encounter the following message:
"libf2c.so.0: undefined symbol: MAIN__ ". Again, the culprit is that
all references must be resolved, and libf2c.so unfortunately contains
a reference to some dummy function. Fortunately the fix is simple,
include the following snippet in your C native source (in our example
mynativecalls.c):

int MAIN__( )
{ return(0);
}

Another solution (not tested) could be to use "-lg2c" instead of
"-lf2c". As I understand it, the g77 runtime library is derived from
the f2c runtime library. An even better (in my opinion) solution would
be to use "f2py" from <http://cens.ioc.ee/projects/f2py2e/>, a tool to
wrap python (and C) code for python.

Regards
Berthold
--
bh***@web.de / http://starship.python.net/crew/bhoel/

[Harry George]

Carl <ph***********@chello.se> writes:

I have experimented with f2c and swig-generated wrappers to create python
modules from Fortran files.

I think I'm missing something when I'm building the Python module, because
when I import the built module the Python interpreter returns the
following:

import LDSsobol

Traceback (most recent call last):
File "<stdin>", line 1, in ?
File "LDSsobol.py", line 4, in ?
import _LDSsobol
ImportError: /usr/lib/libf2c.so.0: undefined symbol: MAIN__

This is how I built LDSsobol:

gcc -c LDSsobol.c
gcc -c LDSsobol_wrap.c -I/usr/include/python
gcc -shared LDSsobol.o LDSsobol_wrap.o -l f2c -o _LDSsobol.so

Any help is appreciated!

Carl

Did you start with pyfort?
http://sourceforge.net/projects/pyfortran

I haven't used it personally, but it seems to be addressing your
concerns, without ad hoc SWIGing.

--
ha************@boeing.com
6-6M21 BCA CompArch Design Engineering
Phone: [phone]

[Fernando Perez]

Carl wrote:

I have experimented with f2c and swig-generated wrappers to create python
modules from Fortran files.

Don't bother, just use f2py. It works beautifully (we use it everyday in
production codes).

Best,

f

[Carl]

> Another solution (not tested) could be to use "-lg2c" instead of

"-lf2c". As I understand it, the g77 runtime library is derived from
the f2c runtime library.
This seems to work! How did you know?
An even better (in my opinion) solution would
be to use "f2py" from <http://cens.ioc.ee/projects/f2py2e/>, a tool to
wrap python (and C) code for python.

I will try both "f2py" and all other possible solution suggestions to my
problem.

I'm positively overwhelmed by your response. You've saved me a great deal of
trouble and (I don't know how many) hours of tedious trial and error work.

Thank you!

Carl