I successfully compiled a shared library for use with CTypes and linked it to an external library (Gnu Scientific Library) on Mac OS X 10.4. I hope this helps Mac people and anyone else who wants to use CTypes to access their own C extensions and use other C libraries in the process. I want to thank several people on this list who gave me many helpful suggestions and asked me good questions. I also want to thank the several people who kept nudging me to try CTypes even though I was reluctant. It is much easier than programming an extension all in C. Below are 4 files that enable building of a C shared library in Mac OS X (10.4) that can be used with CTypes to call a function from the Gnu Scientific Library (a Bessel function program gsl_sf_bessel_J0). You can see that the idea is pretty simple. The code requires that you have ctypes (in site-packages) and GSL (dynlib version in /usr/local/lib) or your desired C library installed. I suspect on other platforms what will be different will be the make file. I do not know enough to provide Linux or Windows versions. I'm sorry. Note: This works best if the libraries are shared (e.g. the GSL library to use is the dynlib version). That way only the code that's needed is loaded when the C functions are called from python. Comments welcome. Of course, I am responsible for any and all mistakes. So, I make no guarantees or warrenties. These are examples and should not be used where loss of property, life, or other dangers exist. #==== Source code 'bess.c' ====================== #include <stdio.h> #include "bess.h" #include <gsl/gsl_sf_bessel.h> /* Must include the header to define the function for compiler */ /* ---- test fcns ------------------------- */ #ifdef __cplusplus extern "C" { #endif double J0_bess (double x) { /* Call the GSL Bessel function order 0 of the first kind */ double y = gsl_sf_bessel_J0 (x); /* Print the value right here */ printf ("J0(%g) = %.18e\n", x, y); return y; } #ifdef __cplusplus } #endif #==== Header file 'bess.h' ===================== /* ---- Prototypes -------------------- */ #ifdef __cplusplus extern "C" { #endif double J0_bess(double x); #ifdef __cplusplus } #endif #==== Make file 'bess.make' =================== # ---- Link to existing library in this directory ------------ bess.so: bess.o bess.mak gcc -bundle -flat_namespace -undefined suppress -o bess.so bess.o -lgsl # ---- gcc C compile ------------------ bess.o: bess.c bess.h bess.mak gcc -c bess.c -o bess.o #==== Python file 'bess.py' ======================= #!/usr/local/bin/pythonw import numpy as N import ctypes as C # Put the name of your library in place of 'bess.so' and the path to # it in place of the path below in load_library _bess = N.ctypeslib.load_library('bess.so', '/Users/loupecora/Code_py/test_folder/ctypes_tests/test3ctypes/simplelink-GSL/') _bess.J0_bess.restype = C.c_double _bess.J0_bess.argtypes = [C.c_double] def fcn_J0(x): return _bess.J0_bess(x) x = 0.2 y = fcn_J0(x) print "x, y: %e %.18e" % (x, y) #==== Typical output =============== # The first line is printed from the shared library function J0_bess # The second line is from the python code that called the shared lib. function J0(0.2) = 9.900249722395765284e-01 x, y: 2.000000e-01 9.900249722395765284e-01 -- Lou Pecora, my views are my own. ____________________________________________________________________________________ Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ