Complete and build the example from the "Using Numpy C-API" documentation.
I would like to take the example shown here: http://docs.scipy.org/doc/numpy/user/c-info.how-to-extend.html#example and complete the code so I can build and test the extension module. Is that example currently correct? It is slightly different from the older example in the numpy book, so someone must have had a reason to change it. I've added the C array of PyMethodDefs and the module init function, but I'm still searching for the correct #includes for the numpy stuff. Any suggestions (or pointers to similar simple but complete examples) would be appreciated. Warren
Warren Weckesser wrote:
I would like to take the example shown here:
http://docs.scipy.org/doc/numpy/user/c-info.how-to-extend.html#example
and complete the code so I can build and test the extension module. Is that example currently correct? It is slightly different from the older example in the numpy book, so someone must have had a reason to change it.
I've added the C array of PyMethodDefs and the module init function, but I'm still searching for the correct #includes for the numpy stuff. Any suggestions (or pointers to similar simple but complete examples) would be appreciated.
I've made some progress, and now I'm getting a bus error. With the following extension module, calling example.foo results in a bus error, regardless of the arguments given. The error occurs in the call to PyArg_ParseTuple. I'm using same format string as in the example in the numpy docs, "O!". Any ideas? ----- #include <stdio.h> #include "Python.h" #include "numpy/arrayobject.h" static PyObject *foo_wrap(PyObject *dummy, PyObject *args) { PyObject *arg1 = NULL; printf("boo\n"); if (!PyArg_ParseTuple(args, "O!", &PyArray_Type, &arg1)) { printf("bad\n"); return NULL; } printf("here\n"); return Py_None; } static PyMethodDef wrappers[] = { {"foo", foo_wrap, METH_VARARGS, "just a test"}, {NULL, NULL, 0, NULL} /* Sentinel */ }; PyMODINIT_FUNC initexample(void) { (void) Py_InitModule("example", wrappers); } -----
Warren
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Tue, 20 Jul 2010 18:04:42 -0500, Warren Weckesser wrote: [clip]
I've made some progress, and now I'm getting a bus error. With the following extension module, calling example.foo results in a bus error, regardless of the arguments given. The error occurs in the call to PyArg_ParseTuple. I'm using same format string as in the example in the numpy docs, "O!". Any ideas?
----- #include <stdio.h> #include "Python.h" #include "numpy/arrayobject.h"
static PyObject *foo_wrap(PyObject *dummy, PyObject *args) { PyObject *arg1 = NULL;
printf("boo\n"); if (!PyArg_ParseTuple(args, "O!", &PyArray_Type, &arg1)) { printf("bad\n"); return NULL; } printf("here\n"); return Py_None; }
You need to INCREF the None return value (but that won't cause a crash here).
static PyMethodDef wrappers[] = { {"foo", foo_wrap, METH_VARARGS, "just a test"}, {NULL, NULL, 0, NULL} /* Sentinel */ };
PyMODINIT_FUNC initexample(void) { (void) Py_InitModule("example", wrappers); }
You need to call import_array(); in the init function. Otherwise, PyArray_Type probably won't be initialized. This can cause a crash. -- Pauli Virtanen
Thanks, Pauli. import_array() is what I was missing. Warren Pauli Virtanen wrote:
Tue, 20 Jul 2010 18:04:42 -0500, Warren Weckesser wrote: [clip]
I've made some progress, and now I'm getting a bus error. With the following extension module, calling example.foo results in a bus error, regardless of the arguments given. The error occurs in the call to PyArg_ParseTuple. I'm using same format string as in the example in the numpy docs, "O!". Any ideas?
----- #include <stdio.h> #include "Python.h" #include "numpy/arrayobject.h"
static PyObject *foo_wrap(PyObject *dummy, PyObject *args) { PyObject *arg1 = NULL;
printf("boo\n"); if (!PyArg_ParseTuple(args, "O!", &PyArray_Type, &arg1)) { printf("bad\n"); return NULL; } printf("here\n"); return Py_None; }
You need to INCREF the None return value (but that won't cause a crash here).
static PyMethodDef wrappers[] = { {"foo", foo_wrap, METH_VARARGS, "just a test"}, {NULL, NULL, 0, NULL} /* Sentinel */ };
PyMODINIT_FUNC initexample(void) { (void) Py_InitModule("example", wrappers); }
You need to call import_array(); in the init function. Otherwise, PyArray_Type probably won't be initialized. This can cause a crash.
participants (2)
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Pauli Virtanen -
Warren Weckesser