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From: Tim Spens <t_spens@yahoo.com>
Subject: Re: embedding and extending python C API registering callback handler objects
To:
python-list@python.org, "Matimus" <mccredie@gmail.com>
Date: Friday, June 27, 2008, 9:16 AM
thanks, but didn't fix the problem.
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--- On Fri, 6/27/08, Matimus <mccredie@gmail.com>
wrote:
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From: Matimus <mccredie@gmail.com>
Subject: Re: embedding and extending python C API
registering callback handler objects
<t_sp...@yahoo.com>
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wrote:
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Hello all,
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I've been trying to get an example found
herehttp://codeidol.com/python/python3/Embedding-Python/Registering-Callb...
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to work. Every thing works fine except when I
try to
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trigger an event from c that will call a python
function.
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Here is my test code:
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//-----------------------python
code--------------------------//
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#! /usr/bin/env python
import time
import callback
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def callback1(label,count):
print 'callback1 successfully
triggered from python via callback.so'
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return 'callback1 =%s number
%i' % (label, count)
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def callback2(label,count):
return 'callback2 =' +
label * count
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print '\nTest1:'
callback.setHandler(callback1)
callback.triggerEvent() # simulate events
caught by C layer
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print '\nTest2:'
callback.setHandler(callback2)
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print 'Waiting for callback2 to be called
from
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c:'
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while 1:
time.sleep(.001)
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//-----------------------c
code-------------------------------//
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#include <Python.h>
#include <stdlib.h>
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/* keep Python object in C */
static PyObject *Handler = NULL;
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void Route_Event(char *label, int count){
char *cres;
PyObject *args, *pres;
/* call Python handler */
args = Py_BuildValue("(si)", label,
count);
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pres = PyEval_CallObject(Handler, args);
Py_DECREF(args);
if (pres != NULL){
/* use and decref handler result */
PyArg_Parse(pres, "s",
&cres);
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printf("%s\n", cres);
Py_DECREF(pres);
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}}
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// the actual python callback call
static PyObject *
make_call(PyObject *function, PyObject *args){
if (function == NULL) return NULL;
PyObject * val =
PyObject_CallObject(function,
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args);
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Py_XDECREF(args);
return val;
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}
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static PyObject *
Register_Handler(PyObject *self, PyObject *args){
/* save Python callable object */
Py_XDECREF(Handler);
PyArg_Parse(args, "O",
&Handler);
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Py_XINCREF(Handler);
Py_INCREF(Py_None);
return Py_None;
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}
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static PyObject *
Trigger_Event(PyObject *self, PyObject *args){
/* let Python simulate event caught by C */
static int count = 0;
Route_Event("spam", count++);
Py_INCREF(Py_None);
return Py_None;
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}
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static struct PyMethodDef callback_methods[] = {
{"setHandler",
Register_Handler},
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/* name, address */
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{"triggerEvent", Trigger_Event},
{NULL, NULL}};
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/* on first "import callback" */
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void initcallback(){ /* this
is called by Python */
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(void) Py_InitModule("callback",
callback_methods);
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}
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int main(){
while (1){
printf("1\n");
//attempting to call callback2
which is registered to Handler
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//i've also tried args =
Py_BuildValue("(si)", label, count); here
but I
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get a segfault.
Py_BuildValue("s","c code");
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printf("2\n");
PyObject* val =
make_call(Handler,args);
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printf("3\n");
Py_XDECREF (val);
printf("4\n");
sleep(1);
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}}
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//------------------------compiler
stuff----------------------//
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gcc callback.c -c -g -Wall -fpic -I
/usr/include/python2.5 -o callback.o
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gcc callback.c -g -Wall -I /usr/include/python2.5
-L
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/usr/local/lib -lpython2.5 -o callback
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gcc -shared -Wall callback.o -o callback.so
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//------------------------test code
results-------------------//
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../callback.py
Test1:
callback1 successfully triggered from python via
callback.so
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callback1 =spam number 0
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Test2:
Waiting for callback2 to be called from c:
#NOTHING EVER GETS PRINTED HERE CALLBACK NEVER
GETS
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CALLED?
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../callback
1
2
3
4
....
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Thanks,
Tim
Maybe you just need to flush the stdout buffer in
python.
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--
http://mail.python.org/mailman/listinfo/python-list I think I know where the problem is but I'm unsure how to fix it. When I call Register_Handler(...) from python via callback.setHandler1(callback1) this only seems to affect pythons ability to trigger an "event" in c. PyObject *Handler is always NULL even after I call Register_Handler(...). I thought there was some magic here that was assigning the pointer *Handler to my python callback1 handler so it could be triggered from c?
