[Numpy-discussion] subclassing array in c

Val Kalatsky kalatsky@gmail....
Wed Mar 7 19:36:39 CST 2012


Tried it on my Ubuntu 10.10 box, no problem:

1) Saved as spampub.c
2) Compiled with (setup.py attached): python setup.py build_ext -i
3) Tested from ipython:
In [1]: import spampub
In [2]: ua=spampub.UnitArray([0,1,2,3.0],'liter')
In [3]: ua
Out[3]: UnitArray([ 0.,  1.,  2.,  3.])
In [4]: ua.unit
Out[4]: 'liter'


On Wed, Mar 7, 2012 at 7:15 PM, Val Kalatsky <kalatsky@gmail.com> wrote:

>
> Seeing the backtrace would be helpful.
> Can you do whatever leads to the segfault
> from python run from gdb?
> Val
>
>
> On Wed, Mar 7, 2012 at 7:04 PM, Christoph Gohle <
> christoph.gohle@mpq.mpg.de> wrote:
>
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA1
>>
>> Hi,
>>
>> I have been struggeling for quite some time now. Desperate as I am, now I
>> need help.
>>
>> I was trying to subclass ndarrays in a c extension (see code below) and
>> do constantly get segfaults. I have been checking my INCREF and DECREF
>> stuff up and down but can't find the error. Probably I got something
>> completely wrong... anybody able to help?
>>
>> Thanks,
>> Christoph
>> - -----------------
>> #include <Python.h>
>> #include <structmember.h>
>>
>> #include <numpy/arrayobject.h>
>>
>> static PyObject *SpamError;
>>
>> typedef struct {
>>  PyArrayObject base;
>>  PyDictObject* unit;
>> } UnitArrayObject;
>>
>> PyTypeObject unitArrayObjectType;
>>
>> static int
>> checkunit(PyObject *unit1, PyObject *unit2) {
>>  return PyObject_Compare(unit1, unit2);
>> }
>>
>> static PyObject *
>> unitArray_new(PyTypeObject *cls, PyObject *args, PyObject *kwargs) {
>>        PyObject *data = NULL,
>>                         *unit = NULL;
>>  PyArray_Descr* dtype = NULL;
>>  PyObject *res = NULL, *tmp = NULL;
>>
>>        if (!PyArg_ParseTuple(args, "OO|O&", &data, &unit,
>> PyArray_DescrConverter, &dtype)) {
>>                Py_XDECREF(dtype);
>>                return NULL;
>>        }
>>
>>  res = PyArray_FromAny(data, dtype, 0, 0, NPY_ENSURECOPY, NULL);
>>        if (res == NULL) {
>>                Py_XDECREF(dtype);
>>    //TODO: raise exception?
>>                return NULL;
>>        }
>>
>>        if (PyObject_IsInstance(data, (PyObject*)cls)) {
>>                if (unit!=NULL &&
>> !checkunit((PyObject*)((UnitArrayObject*)data)->unit,unit)) {
>>                        Py_XDECREF(res);
>>                        //TODO: raise exception
>>                        return NULL;
>>                }
>>        } else {
>>                if (PyObject_IsTrue(unit)) {
>>      tmp = res;
>>                        res = PyArray_View((PyArrayObject*)res, NULL,
>> &unitArrayObjectType);
>>      if (tmp!=res) {
>>        Py_XDECREF(tmp);
>>      }
>>      ((UnitArrayObject*)res)->unit = (PyDictObject*)unit;
>>      Py_INCREF(unit);
>>      if (unit!=NULL) {
>>      }
>>                }
>>        }
>>        return res;
>> }
>>
>> static PyObject*
>> unitArray__array_finalize__(PyObject* new, PyObject* args) {
>>        PyObject *attr = NULL, *tmp = NULL;
>>  PyObject *parent = NULL;
>>
>>  if (!PyArg_ParseTuple(args, "O", &parent)) {
>>    return NULL;
>>  }
>>   if (parent!=NULL) {
>>     attr = PyObject_GetAttrString(parent, "unit");
>>     if (attr == NULL) {
>>        //parent has no 'unit' so we make a new empty one
>>       attr = PyDict_New();
>>       PyErr_Clear();
>>     }
>>   }
>>  tmp = (PyObject*)((UnitArrayObject*)new)->unit;
>>    ((UnitArrayObject*)new)->unit = (PyDictObject*)attr;
>>
>>  Py_INCREF(Py_None);
>>  return Py_None;
>> }
>>
>> static PyObject*
>> unitArray__array_wrap__(PyObject *self, PyObject *args) {
>>        PyObject *array = NULL, *context = NULL;
>>
>>        if (!PyArg_ParseTuple(args, "OO", array, context)) {
>>                //TODO: raise exception
>>                return NULL;
>>        }
>>
>>        printf("%s",PyString_AsString(PyObject_Str(context)));
>>
>>  Py_INCREF(array);
>>  return array;
>> }
>>
>>
>> static PyMethodDef unitArrayMethods[] = {
>>  {"__array_finalize__", unitArray__array_finalize__, METH_VARARGS, "array
>> finalize method"},
>>  {"__array_wrap__", unitArray__array_wrap__, METH_VARARGS, "array wrap
>> method"},
>>  {NULL, NULL, 0, NULL}
>> };
>>
>> static PyMemberDef unitArrayMembers[] = {
>>  {"unit", T_OBJECT, offsetof(UnitArrayObject, unit),  0, "dictionary
>> containing unit info."},
>>  {NULL, 0, 0, 0, NULL}
>> };
>>
>> PyTypeObject unitArrayObjectType = {
>>        PyObject_HEAD_INIT(NULL)
>>        0,                              /* ob_size        */
>>        "spam.UnitArray",               /* tp_name        */
>>        sizeof(UnitArrayObject),                /* tp_basicsize   */
>>        0,                              /* tp_itemsize    */
>>        0,                              /* tp_dealloc     */
>>        0,                              /* tp_print       */
>>        0,                              /* tp_getattr     */
>>        0,                              /* tp_setattr     */
>>        0,                              /* tp_compare     */
>>        0,                              /* tp_repr        */
>>        0,                              /* tp_as_number   */
>>        0,                              /* tp_as_sequence */
>>        0,                              /* tp_as_mapping  */
>>        0,                              /* tp_hash        */
>>        0,                              /* tp_call        */
>>        0,                              /* tp_str         */
>>        0,                              /* tp_getattro    */
>>        0,                              /* tp_setattro    */
>>        0,                              /* tp_as_buffer   */
>>        Py_TPFLAGS_DEFAULT,             /* tp_flags       */
>>        "A numpy array with units",     /* tp_doc         */
>>  0,        /* traverseproc */
>>  0,        /* tp_clear*/
>>  0,        /* tp_richcompare */
>>  0,        /* tp_weaklistoffset */
>>  0,        /* tp_iter */
>>  0,        /* tp_iternext */
>>  unitArrayMethods,        /* tp_methods */
>>  unitArrayMembers,        /* tp_members */
>>  0,        /* tp_getset */
>>  0,        /* tp_base*/
>>  0,        /* tp_dict */
>>  0,        /* tp_descr_get*/
>>  0,        /* tp_descr_set */
>>  0,        /* tp_dictoffset */
>>  0,        /* tp_init */
>>  0,        /* tp_alloc */
>>  unitArray_new /* tp_new */
>> };
>>
>>
>> static PyMethodDef SpamMethods[] = {
>>    {NULL, NULL, 0, NULL}        /* Sentinel */
>> };
>>
>> PyObject *unitArray = NULL;
>> PyMODINIT_FUNC
>> initspampub(void)
>> {
>>  import_array();
>>
>>  PyObject *m;
>>
>>  Py_INCREF(&PyArray_Type);
>>  unitArrayObjectType.tp_base = &PyArray_Type;
>>
>>  if (PyType_Ready(&unitArrayObjectType) < 0)
>>    return;
>>
>>
>>  m = Py_InitModule3("spampub", SpamMethods, "some tests and a array type
>> with units.");
>>  if (m == NULL)
>>    return;
>>
>>  SpamError = PyErr_NewException("spampub.error", NULL, NULL);
>>  Py_INCREF(SpamError);
>>  PyModule_AddObject(m, "error", SpamError);
>>  Py_INCREF(&unitArrayObjectType);
>>  PyModule_AddObject(m, "UnitArray", (PyObject *)&unitArrayObjectType);
>>  (void) Py_InitModule("spampub", SpamMethods);
>>
>> }
>>
>>
>> -----BEGIN PGP SIGNATURE-----
>> Version: GnuPG/MacGPG2 v2.0.14 (Darwin)
>>
>> iEYEARECAAYFAk9YBbkACgkQLYu25rCEIzsExQCggHg0e0ibYP3bEsAE0Ce8Rbm3
>> qOcAoKwuTuE4BDZgrqNpwISgMS6uSMnO
>> =Qtek
>> -----END PGP SIGNATURE-----
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>
>
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