[ctypes-users] Ctypes in numpy

[Gael V. <gae...@no...>]

    Hi all,

I am totally new to ctypes. I am not exactly an expert porgramer: I am
physicist who always gets asked to solve peoples problems. My current
problem is that I would like to interface a camera with python (numpy to
be precise). I have the SDK of the camera, and C++ functions and classes
to use for the interfacing. I have sorted out how to control the camera
from C++, and now I want to find out how to control the C++ from python.
First thing I do is try Albert Strasheim's example on
http://scipy.org/Cookbook/Ctypes2 . I am trying this out on Ubuntu
Dapper with Andrew Straw's Numpy packages (numpy version 1.0b5). I did
pure copy and paste of Albert's examples (including the Sconstruct
file). Compilation with scons went fine, but the python call to
loadlibrary doesn't work:

In [4]: import numpy as N

In [5]: _foo =3D N.ctypeslib.load_library('foo', '.')
-------------------------------------------------------------------------=
--
exceptions.OSError                                   Traceback (most
recent call last)

/home/varoquau/work/toronto/bin/ctypes/<ipython console>

/usr/lib/python2.4/site-packages/numpy/ctypeslib.py in
load_library(libname, loader_path)
     21     import ctypes
     22     libpath =3D os.path.join(libdir, libname)
---> 23     return ctypes.cdll[libpath]
     24
     25 def _num_fromflags(flaglist):

/usr/lib/python2.4/site-packages/ctypes/__init__.py in __getitem__(self,
name)
    424
    425     def __getitem__(self, name):
--> 426         return getattr(self, name)
    427
    428     def LoadLibrary(self, name):

/usr/lib/python2.4/site-packages/ctypes/__init__.py in __getattr__(self,
name)
    419             raise AttributeError, name
    420         libpath =3D find_library(name)
--> 421         dll =3D self._dlltype(libpath)
    422         setattr(self, name, dll)
    423         return dll

/usr/lib/python2.4/site-packages/ctypes/__init__.py in __init__(self,
name, handle, mode)
    329         self._name =3D name
    330         if handle is None:
--> 331             self._handle =3D _LoadLibrary(self._name, mode)
    332         else:
    333             self._handle =3D handle

OSError: lib/home/varoquau/work/toronto/bin/ctypes/foo.so.so: cannot
open shared object file: No such file or directory

In [6]:


Strangely enough, in my current directory I don't have a foo.so.so, I do
have a libfoo.so. So just to check I do a symlink from foo.so.so to
libfoo.so, but I get the same error message.

I am sure this problem probably has a very simple answer. Could you give
me a hand debugging this ?

Cheers,

Ga=EBl