[Numpy-discussion] Calling routines from a Fortran library using python

Nils Wagner nwagner@iam.uni-stuttgart...
Tue Feb 23 02:43:04 CST 2010


On Mon, 22 Feb 2010 22:18:23 +0900
  David Cournapeau <cournape@gmail.com> wrote:
> On Mon, Feb 22, 2010 at 10:01 PM, Nils Wagner
> <nwagner@iam.uni-stuttgart.de> wrote:
> 
>>
>> ar x test.a
>> gfortran -shared *.o -o libtest.so -lg2c
>>
>> to build a shared library. The additional option -lg2c 
>>was
>> necessary due to an undefined symbol: s_cmp
> 
> You should avoid the -lg2c option at any cost if 
>compiling with
> gfortran. I am afraid that you got a library compiled 
>with g77. If
> that's the case, you should use g77 and not gfortran. 
>You cannot mix
> libraries built with one with libraries with another.
> 
>>
>> Now I am able to load the shared library
>>
>> from ctypes import *
>> my_lib = CDLL('test.so')
>>
>> What are the next steps to use the library functions
>> within python ?
> 
> You use it as you would use a C library:
> 
> http://python.net/crew/theller/ctypes/tutorial.html
> 
> But the fortran ABI, at least for code built with g77 
>and gfortran,
> pass everything by reference. To make sure to pass the 
>right
> arguments, I strongly suggest to double check with the 
>.h you
> received.
> 
> cheers,
> 
> David
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Just to play it safe

Consider

extern void	dsio	(int* const,const char* const,
			 int* const,const size_t);
extern void	dsrhed	(const int* const,const int* 
const,void* const,
			 const int* const,const int* const,int* const,
			 int* const,int* const,int* const,int* const,
			 int* const,int* const,int* const);
  


from ctypes import *
my_lib = CDLL('libtest.so')

How do I call the functions within python
I mean what arguments are needed ?

my_lib.dsio(    )

my_lib.dsrhed(   )

Thank you very much for your help.

Cheers,
                    Nils


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