Nested/Sub Extensions in Python

[H Linux]

Dear all,

I am currently fighting with a problem writing a set of Python
extensions in C. I want to structure the whole package (here called
smt for sub-module test) into different sub-modules, e.g. according to
this layout:

smt.foo.func()

I can only build a module
>import foo
>print foo.func(1,2)

Once I try to nest this, I cannot get the module to load anymore:
>import smt.bar
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named bar

I have found the following hints on the web:
http://stackoverflow.com/questions/1681281/nested-python-c-extensions-modules
I have also found that XEN has a python module which does this, but
http://www.google.de/codesearch#4Wqoij9clTg/tools/python/setup.py

Still I am unable to get this to work. What am I missing? In case it
matters, this is on Ubuntu10.4/Python2.6.5 Below are listings from my
source files.

Thanks in advance for any help,
Hartwig


1. setup.py:
from distutils.core import setup, Extension
PACKAGE_NAME = 'smt'
setup(
    name         = PACKAGE_NAME,
    version      = '0.1',
    author       = 'Myself',
    packages     = [PACKAGE_NAME],
    ext_modules  = [ Extension('foo',     ['src/foo.c']),
                     Extension('smt.bar', ['src/bar.c'])  ]
)

2. src/bar.c
#include <Python.h>

static PyObject*
bar_func(PyObject *self, PyObject *args)
{
	PyObject *a, *b;

	if (!PyArg_UnpackTuple(args, "func", 2, 2, &a, &b)) {
		return NULL;
	}

	return PyNumber_Add(a, b);
}

static PyMethodDef bar_methods[] = {
  {"func", bar_func, METH_VARARGS, NULL},
	{NULL, NULL}
};

PyMODINIT_FUNC
initbar(void)
{
	Py_InitModule("smt.bar", bar_methods);
}

3. src/foo.c
#include <Python.h>

static PyObject*
foo_func(PyObject *self, PyObject *args)
{
	PyObject *a, *b;
	if (!PyArg_UnpackTuple(args, "func", 2, 2, &a, &b)) {
		return NULL;
	}
	return PyNumber_Add(a, b);
}

static PyMethodDef foo_methods[] = {
	{"func", foo_func, METH_VARARGS, NULL},
	{NULL, NULL}
};

PyMODINIT_FUNC
initfoo(void)
{
	Py_InitModule("foo", foo_methods);
}

4. Code Layout:
├── setup.py
├── smt
│   └── __init__.py
└── src
    ├── bar.c
    └── foo.c