On Wed, 04 Jun 2008 05:57:20 -0700, spectrumdt wrote:
> Hello.
>
> I am trying to extend Python with some C code. I made a trivial
> "Hello World" program in C that I am trying to wrap in "boilerplate" for
> inclusion in a Python program. But I can't compile the C code. The C
> compiler cannot find the required function `Py_BuildValue'.
>
> My C code looks like this:
>
>
>
> #include "/usr/include/python2.5/Python.h"
>
> /* Python wrapper for 'main'. */
> static PyObject* mpi_main() {
> int res = main();
> PyObject* retval = (PyObject*)Py_BuildValue("i",res);
> }
>
> /* Main. A 'Hello World' function. */ int main() {
> printf ("Hello, World. I am a C function.\n");
> }
>
>
>
> And my error message looks like this:
>
>
>
> [EMAIL PROTECTED] Opgave03]$ gcc ctest.c /tmp/ccH46bs8.o: In function
> `mpi_main': ctest.c:(.text+0x1d): undefined reference to
> `Py_BuildValue' collect2: ld returned 1 exit status
> [EMAIL PROTECTED] Opgave03]$
>
>
>
> I searched the newsgroup and found this thread:
>
>
> http://groups.google.com/group/comp.lang.python/browse_thread/thread/
c6d70e02a6bc9528/87b836f369bd0042?lnk=gst&q=undefined+reference+to+%
60Py_BuildValue%27#87b836f369bd0042
>
> It recommended that I add the option "-Wl,--export-dynamic" when
> calling gcc. That makes no difference. The thread also has some more
> stuff that I don't quite understand.
>
> Can anyone help? I am including Python.h, so why does it not find
> Py_BuildValue?
>
> Thanks in advance.
Hi! Your C code contains too many errors. I'm lazy to comment them all.
Here's my take on the trivial "Hello world" in Python C API:
1. create 'hello.c' file with the following content:
#include <Python.h>
PyObject*
hello(PyObject* self)
{
printf("Hello world!\n");
Py_RETURN_NONE;
}
static PyMethodDef functions[] = {
{"hello", (PyCFunction)hello, METH_NOARGS},
{NULL, NULL, 0, NULL},
};
DL_EXPORT(void)
init_hello(void)
{
Py_InitModule("_hello", functions);
}
2. create 'buildme.py' file with this content:
import os
import sys
from distutils.core import Extension, setup
os.chdir(os.path.dirname(os.path.abspath(__file__)))
sys.argv = [sys.argv[0], 'build_ext', '-i']
setup(ext_modules = [Extension('_hello', ["hello.c"])])
3. run "python buildme.py"
That's all.
>>> from _hello import hello
>>> hello()
Hello world!
-- Ivan
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