En Thu, 08 Mar 2007 22:26:59 -0300, ZiZi Zhao <[EMAIL PROTECTED]> escribió:
> I tried to build a list of dictionaries using embedded Python2.5
> in the following way to append dictionaries to a list.
>
> Py_Object *pList = PyList_New(0);
>
> for (i=0; i<MAXSIZE; i++) {
> Py_Object *pDict = PyDict_New();
> //
> // build this dictionary of keys & values
> //
> if (pDict != NULL) {
> if (PyList_Append(pList, pDict) < 0) {
> printf ("Failed to append new dict to dict-list\n");
> }
> Py_DECREF(pDict);
> }
> }
>
> In this way, I found the PyList_Append only appends the pointer
> of pDict to pList.
All Python objects are seen as pointers on C code.
> After Py_DECREF(pDict) and going back to,
> Py_Object *pDict = PyDict_New();
> for next run in loop, it gets the same pointer as last time,
Perhaps (in the non-posted block) there is a Py_INCREF missing, and that
last Py_DECREF destroys the object.
(You don't see the printf message, I presume)
> which finally makes all dictionaries in the list are the same
> as the last one. (BTW, in Python, the result is correct.)
> Now, I have to do no Py_DECREF(pDict) in the loop, but do once at
> the end, when the loop is finished, like
You could check using sys.getrefcount; if all of them say 2 (including the
last dict) you know the list holds the only reference to them. (And all
id() should be different, too).
Maybe this code is useful; builds a list of empty dictionaries. (Note that
I *know* the list is empty and has the right size, so I can use
PyList_SET_ITEM instead of the non-macro version PyList_SetItem or the
insert/append variants).
/*
flistdict - fast list of dictionaries
flistdict(size) -> [{},{},...] = [{} for _ in range(size)]
Devuelve una lista de diccionarios vacíos (todos diferentes)
*/
static PyObject *
flistdict(PyObject *self, PyObject *args)
{
int i, size;
PyObject *result=NULL, *dict=NULL;
if (!PyArg_ParseTuple(args, "i", &size))
return NULL;
result = PyList_New(size);
if (result==NULL)
goto error;
for (i=0; i<size; i++) {
dict = PyDict_New();
if (dict==NULL)
goto error;
PyList_SET_ITEM(result, i, dict);
}
goto normalexit;
error:
Py_XDECREF(result);
result = NULL;
normalexit:
return result;
}
--
Gabriel Genellina
--
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