Python C Extensions

aken8062 at yahoo.com aken8062 at yahoo.com
Thu Feb 24 17:46:57 CET 2011


Thank you very much, it worked.
I thought the PyDict_SetItem should assume ownership
of the passed object and decrease it's reference count (I do not know
why).

Does this also go for the Lists ? Should anything inserted into list
also
be DECRED-ed ?

Thank you again for reply.

On Feb 24, 11:33 am, MRAB <pyt... at mrabarnett.plus.com> wrote:
> On 24/02/2011 16:01, aken8... at yahoo.com wrote:
>
>
>
>
>
> > Hi,
>
> > I have a memory leak problem with my "C" extension module. My C module
> > returns large dictionaries to python, and the dictionaries never get
> > deleted, so the memory for my program keeps growing.
>
> > I do not know how to delete the dictionary object after it becomes
> > irrelevant. I do not know if the version of python is relevant, I'm
> > using the 2.5 !
>
> > Here is the "C" code:
>
> > PyObject *GetDictionary(PyObject *self, PyObject *args)
> > {
> >    PyObject *dict = PyDict_New();
> >    PyObject *key;
> >    PyObject *value;
>
> >    char name[128];
>
> >    for(int i = 0; i<  60; i++)
> >      {
> >        sprintf(name,"v%d",i);
> >        float number = 1.0 * 0.5*i;
>
> > PyDict_SetItem(dict,Py_BuildValue("s",name),Py_BuildValue("f",number));
> >      }
> >    return dict;
> > }
>
> > And here is the Code that I use in a loop, which causes the program
> > memory to grow:
> > import libpyTestModule as pyTEST
>
> > bankTEST = {}
> > for j in range(1,100000):
> >      for k in range(1,100000):
> >          bankTEST = pyTEST.GetDictionary()
> >          del bankTEST
>
> > Any help will be appreciated.
>
> Py_BuildValue(...) returns an object with its refcount set to 1.
>
> PyDict_SetItem(...) increments the refcounts of the key and value
> objects when they are added to the dict, so their refcounts will then
> be 2.
>
> When the dict is garbage-collected the refcouts of the key and value
> objects will be decremented to 1, so they won't be collected, and as
> there aren't any other references to them, leading to a memory leak.
>
> You therefore need to decrement the refcounts of the key and value
> objects after adding them to the dict:
>
>      PyObject *key = Py_BuildValue("s", name);
>      PyObject *value = Py_BuildValue("f", number);
>      PyDict_SetItem(dict, key, value);
>      Py_DECREF(key);
>      Py_DECREF(value);




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