PyArg_ParseTupleAndKeywords in Python3.1

[Joachim Dahl]

thanks - the patch fixed my problem.

Joachim

On Dec 1, 5:51 am, casevh <cas... at gmail.com> wrote:
> On Nov 30, 2:18 pm, Joachim Dahl <dahl.joac... at gmail.com> wrote:
>
>
>
>
>
> > I think that "C" encoding is what I need, however I run into an odd
> > problem.
> > If I use the following C code
>
> > static PyObject* foo(PyObject *self, PyObject *args, PyObject *kwrds)
> > {
> >   char a, b;
> >   char *kwlist[] = {"a", "b", NULL};
> >   if (!PyArg_ParseTupleAndKeywords(args, kwrds, "|CC", kwlist, &a,
> > &b))
> >     return NULL;
> >   ...
>
> > then the following works:
>
> > >>> foo('a')
> > >>> foo('a','b')
> > >>> foo(a='a',b='b')
>
> > but the following fails:>>> foo(b='b')
>
> > RuntimeError: impossible<bad format char>: 'CC'
>
> > Is this error-message expected?
>
> Nope. It appears to be a bug in Python. The format code 'C' is missing
> in the switch statement in skipitem() in getargs.c. I added "case
> 'C': /* int */" after "case 'c': /* char */" and then example worked
> for me.
>
> I'll open a bug report.
>
> casevh
>
>
>
>
>
> > On Nov 30, 10:19 pm, casevh <cas... at gmail.com> wrote:
>
> > > On Nov 30, 1:04 pm, Joachim Dahl <dahl.joac... at gmail.com> wrote:
>
> > > > Obviously the name of the C function and the char variable cannot both
> > > > be foo,
> > > > so the C code should be:
>
> > > > static PyObject* foo(PyObject *self, PyObject *args, PyObject *kwrds)
> > > > {
> > > >   char foochar;
> > > >   char *kwlist[] = {"foochar", NULL};
> > > >   if (!PyArg_ParseTupleAndKeywords(args, kwrds, "c", kwlist,
> > > > &foochar))
> > > >     return NULL;
> > > >   ...
>
> > > > The question remains the same: why can't I pass a single character
> > > > argument to this function under Python3.1?
>
> > > > Thanks.
> > > > Joachim
>
> > > > On Nov 30, 9:52 pm, Joachim Dahl <dahl.joac... at gmail.com> wrote:
>
> > > > > I am updating an extension module from Python2.6 to Python3.
>
> > > > > I used to pass character codes to the extension module, for example, I
> > > > > would write:
>
> > > > > >>> foo('X')
>
> > > > > with the corresponding C extension routine defined as follows:
> > > > > static PyObject* foo(PyObject *self, PyObject *args, PyObject *kwrds)
> > > > > {
> > > > >   char foo;
> > > > >   char *kwlist[] = {"foo", NULL};
> > > > >   if (!PyArg_ParseTupleAndKeywords(args, kwrds, "c", kwlist, &foo))
> > > > >     return NULL;
> > > > >   ...
>
> > > > > In Python3.0 this also works, but in Python3.1 I get the following
> > > > > error:
> > > > > TypeError: argument 1 must be a byte string of length 1, not str
>
> > > > > and I seem to be supposed to write>>> foo(b'X')
>
> > > > > instead. From the Python C API, I have not been able to explain this
> > > > > new behavior.
> > > > > What is the correct way to pass a single character argument to
> > > > > Python3.1
> > > > > extension modules?- Hide quoted text -
>
> > > > - Show quoted text -
>
> > > Python 3.1 uses "c" (lowercase c) to parse a single character from a
> > > byte-string and uses "C" (uppercase c) to parse a single character
> > > from a Unicode string. I don't think there is an easy way to accept a
> > > character from both.
>
> > > HTH,
>
> > > casevh