PyArg_ParseTuple, test for SEVERAL possibilities

[Torsten Mohr]

Hi,

i'd like to write an extension module and use
PyArg_ParseTuple in that to parse the parameters.

I have several questions related to this that i did
not find in the documentation:

1. I'd like to check for a list of "int"s and i don't
know how many int's are in this array, it could be
0 to 8, all of this would make sense.

How can i check for that?
2. I'd like to check for SEVERAL possibilities of
argument string, e.g. for "sss" and "li" and "[3]".
How can i do that without error message when the
parameters do not match?
3. Not really related to ParseTuple, but to BuildValue:
I want to create a list as a return value. I want to
create the size of that list at runtime.
For example if i want to return a list with up to
200 values, how can i build that at runtime?
I'm sorry if i missed something, but i read the documentation
and googled for it. But sadly no results...
Best regards,
Torsten.

[Skip Montanaro]

Torsten> 1. I'd like to check for a list of "int"s and i don't
Torsten> know how many int's are in this array, it could be
Torsten> 0 to 8, all of this would make sense.

Torsten> How can i check for that?

How about:

/* define my int args with desired default values */
int i1 = 0, i2 = 0, ..., i8 = 0;

if (!PyArg_ParseTuple(args, "|iiiiiiii", &i1, &i2, ..., &i8) {
return NULL;
}

/* do stuff with i1 ... i8 */

Torsten> 2. I'd like to check for SEVERAL possibilities of
Torsten> argument string, e.g. for "sss" and "li" and "[3]".
Torsten> How can i do that without error message when the
Torsten> parameters do not match?

Just call PyArg_ParseTuple repeatedly until one variant works. Call
PyErr_Clear() before each call. After the last possibility if it still
fails, suppress that last error and raise your own error which will make
more sense than the generic message in the raised exception.

Torsten> 3. Not really related to ParseTuple, but to BuildValue:
Torsten> I want to create a list as a return value. I want to
Torsten> create the size of that list at runtime.
Torsten> For example if i want to return a list with up to
Torsten> 200 values, how can i build that at runtime?

This would be

mylist = PyList_New(0);
if (!mylist) { handle error }

/* append up to 200 values to the list */

In other words, you probably don't want to you Py_BuildValue for this.

Skip