This is becoming utterly painful process.... I found out that the return
value from "format_exception" function is NOT a list, i.e. PyList_Check()
fails. PySequence_Check() succeeds but then PySequence_List() gives me
back -1. So wtf?
I must say the API is crap on this part. Im trying to get error
information regarding previous error and if all i get back is another
error indicator, then what am I supposed to do? Recursive error handling?
Sounds like da bomb!
The API should have two levels of error handling. First level should
expose a conventional error code mechanism for checking for bad params
etc. Only if the error code says that there was a python error during
evaluation/compilation should one need to use this mechanism.
Just my two cents.
Thanks for help.
void get_python_error_info(string& info)
{
GIL g;
PyObject* type = NULL;
PyObject* value = NULL;
PyObject* trace = NULL;
PyErr_Fetch(&type, &value, &trace);
py_ref ref_type(type);
py_ref ref_value(value);
py_ref ref_trace(trace);
py_ref name(PyString_FromString("traceback"));
py_ref module(PyImport_Import(name.get()));
if (!module)
{
PyErr_Clear();
return;
}
PyObject* list = NULL;
if (trace)
{
py_ref fun(PyObject_GetAttrString(module.get(), "format_exception"));
if (fun)
list = PyObject_CallFunctionObjArgs(type, value, trace, NULL);
PyErr_Clear();
}
else
{
py_ref fun(PyObject_GetAttrString(module.get(),
"format_exception_only"));
if (fun)
list = PyObject_CallFunctionObjArgs(type, value, NULL);
PyErr_Clear();
}
if (list && PySequence_Check(list))
{
Py_ssize_t len = PySequence_Size(list);
for (Py_ssize_t i=0; i<len; ++i)
{
// bla bla
}
}
Py_XDECREF(list);
PyErr_Clear();
}
> Hello group,
>
> I'm trying to get the Python exception information (message and
> traceback)
> stored into a string in my C++ code. However all i get back is the string
> "None".
This is what you get (actually "None\n") when there is no error set.
> All the checks pass and all pointers get a value from the python
> API calls. I've also tried with a different function such as
> PyObject_CallFunctionObjArgs but the result is the same.
Since you already know the three components (type, value, trace), I'd use
traceback.format_exception instead (and remove the PyErr_Restore call -
I'm unsure if it works the way you expect it).
In this case you have to pass three arguments, so yes, use
PyObject_CallFunctionObjArgs (remember the final NULL). Beware:
format_exception returns a formatted list, not a string. You have to
concatenate all the elements (either using ''.join or repeteadly calling
PyString_Concat)
> void get_python_exception(string& message, string& traceback)
> {
> GIL g;
> PyObject* type = NULL;
> PyObject* value = NULL;
> PyObject* trace = NULL;
> PyErr_Fetch(&type, &value, &trace);
> py_ref ref_type(type);
> py_ref ref_value(value);
> py_ref ref_trace(trace);
> py_ref name(PyString_FromString("traceback"));
> py_ref module(PyImport_Import(name.get()));
> if (module)
> {
> py_ref fun(PyObject_GetAttrString(module.get(), "format_exc"));
> if (fun)
> {
> PyErr_Restore(type, value, trace);
> ref_type.release();
> ref_value.release();
> ref_trace.release();
> py_ref ret(PyObject_CallObject(fun.get(), NULL));
> if (ret && PyString_Check(ret.get()))
> {
> char* str = PyString_AsString(ret.get());
> message = str;
> traceback = "traceback not available";
> return;
> }
> }
> }
> message = "message not available";
> traceback = "traceback not available";
> }
--
Gabriel Genellina
--
http://mail.python.org/mailman/listinfo/python-list
