SystemError: new style getargs format but argument is not a tuple

[zefciu]

I am trying to embed a c function in my python script for a first time.
When I try to call it I get an error

SystemError: new style getargs format but argument is not a tuple

Guido said on some mailing list, that it is probably an effect of the
lack of METH_VARARGS in the functions' array, but it's ok in my source
code. Here is the full code:

#include <python2.4/Python.h>

static PyObject * mandelpixel(PyO bject *self, PyObject *args)
{
double z_real = 0, z_imag = 0, z_real2 = 0, z_imag2 = 0, c_real,
c_imag, bailoutsquare;
int iteration_numbe r;
register int i;
PyObject coord;
if (!PyArg_ParseTu ple(args, "Oid", &coord, &iteration_numb er,
&bailoutsquare) )
return NULL;
if (!PyArg_ParseTu ple(&coord, "dd", &c_real, &c_imag))
return NULL;

for(i = 1; i <= iteration_numbe r; i++)
{
z_imag = 2 * z_real * z_imag + c_imag;
z_real = z_real2 - z_imag2 + c_real;
z_real2 = z_real * z_real;
z_imag2 = z_imag * z_imag;
if (z_real2 + z_imag2 bailoutsquare)
return Py_BuildValue(" i", i);
}
return Py_BuildValue(" i", 0);
}

static PyMethodDef MandelcMethods[] =
{
{
"mandelpixe l", mandelpixel, METH_VARARGS, "check the pixel for
Mandelbrot set"
},
{
NULL, NULL, 0, NULL
}
};

PyMODINIT_FUNC initmandelc(voi d)
{
(void) Py_InitModule ("mandelc", MandelcMethods) ;
}

int main(int argc, char **argv)
{
Py_SetProgramNa me(argv[0]);
Py_Initialize() ;
initmandelc();
return 0;
}

Greets
zefciu

[Ziga Seilnacht]

zefciu wrote:

Ok. Now I do it this way:

c_real = PyFloat_AsDoubl e(PyTuple_GetIt em(coord,0));
c_imag = PyFloat_AsDoubl e(PyTuple_GetIt em(coord,1));

And it worked... once. The problem is really funny - in the interactive
the function fails every second time.

>mandelpixel((1 .5, 1.5), 9, 2.2)

args parsed
coord parsed
ii3>>mandelpixe l((1.5, 1.5), 9, 2.2)

TypeError: bad argument type for built-in operation>>mand elpixel((1.5, 1.5), 9, 2.2)

args parsed
coord parsed
ii3>>mandelpixe l((1.5, 1.5), 9, 2.2)

TypeError: bad argument type for built-in operation

etcaetera.... (the "args parsed" "coord parsed" and "i" are effect of
printfs in the code, as you see when it fails, it doesn't even manage to
parse the arguments.

The direct solution to your problem is to use the "tuple unpacking"
feature of PyArg_ParseTupl e by using "(dd)id" as format argument.
This is shown in the first example.
The second example uses your approach and is a bit more cumbersome,
but still works. Could you post your current version of the code?
I don't understand where your problem could be.

#include "Python.h"

static PyObject *
mandelpixel1(Py Object *self, PyObject *args)
{
double z_real = 0, z_imag = 0, z_real2 = 0, z_imag2 = 0;
double c_real, c_imag, bailoutsquare;
int iteration_numbe r;
register int i;

if (!PyArg_ParseTu ple(args, "(dd)id", &c_real, &c_imag,
&iteration_numb er, &bailoutsquare) )
return NULL;

for (i = 1; i <= iteration_numbe r; i++) {
z_imag = 2 * z_real * z_imag + c_imag;
z_real = z_real2 - z_imag2 + c_real;
z_real2 = z_real * z_real;
z_imag2 = z_imag * z_imag;
if (z_real2 + z_imag2 bailoutsquare)
return Py_BuildValue(" i", i);
}

return Py_BuildValue(" i", 0);
}

static PyObject *
mandelpixel2(Py Object *self, PyObject *args)
{
double z_real = 0, z_imag = 0, z_real2 = 0, z_imag2 = 0;
double c_real, c_imag, bailoutsquare;
int iteration_numbe r;
PyObject *coord;
register int i;

if (!PyArg_ParseTu ple(args, "Oid", &coord,
&iteration_numb er, &bailoutsquare) )
return NULL;
if (!PyTuple_Check (coord)) {
PyErr_SetString (PyExc_TypeErro r, "something informative");
return NULL;
}

if (!PyArg_ParseTu ple(coord, "dd", &c_real, &c_imag))
return NULL;

for (i = 1; i <= iteration_numbe r; i++) {
z_imag = 2 * z_real * z_imag + c_imag;
z_real = z_real2 - z_imag2 + c_real;
z_real2 = z_real * z_real;
z_imag2 = z_imag * z_imag;
if (z_real2 + z_imag2 bailoutsquare)
return Py_BuildValue(" i", i);
}

return Py_BuildValue(" i", 0);
}

static PyMethodDef MandelcMethods[] = {
{"mandelpixel1" , mandelpixel1, METH_VARARGS, "first version"},
{"mandelpixel2" , mandelpixel2, METH_VARARGS, "second version"},
{NULL, NULL, 0, NULL},
};

PyMODINIT_FUNC
initmandelc(voi d)
{
Py_InitModule(" mandelc", MandelcMethods) ;
}

Ziga

[zefciu]

Ziga Seilnacht wrote:

The second example uses your approach and is a bit more cumbersome,
but still works. Could you post your current version of the code?
I don't understand where your problem could be.

I think, there's no need to. Now I understand :)

if (!PyArg_ParseTu ple(args, "Oid", &coord,
&iteration_numb er, &bailoutsquare) )

There was no ampersand in my version before coord. I thought that as
coord is already a pointer, PyArg_ParseTupl e will want it, not the
pointer to the pointer.

Now it works, but I will of course change it to get the simpler
parenthesised version as in your Example 1.

Great thanks :D

zefciu