Passing python list from C to python

[hartley]

On Jul 13, 6:35 pm, John Machin <sjmac... at lexicon.net> wrote:
> On Jul 14, 1:47 am, hartley <hartle... at gmail.com> wrote:
>
>
>
> > I'm very new at wrapping Python/C, and I have run into some problems.
>
> > I have one python module that provides me with a list (provideBuffer
> > in provideBuff.py):
>
> >  Py_Initialize();
> >         pName = PyString_FromString("provideBuff");
> >         pModule = PyImport_Import(pName);
>
> >         pFunc = PyObject_GetAttrString(pModule,"provideBuffer");
>
> >         pValue = PyObject_CallObject(pFunc,NULL);
>
> > pValue is now a PyList - i've even verified this with:
>
> > int a = PyList_Check(pValue);
> >         printf("%d\n", a);
>
> > However, I want to send this PyList to another python module,
>
> Please explain "send" ... do you mean the C equivalent of the Python
> statement C_embedding.buff = the_pylist ?
>
> BTW C-embedding would trigger a syntax error in Python source; best to
> avoid ...
>
> > but I
> > don't know how to do this. Initially I though I could just do like
> > above, only swapping NULL with pValue, but that is not working.
>
> > pName2 = PyString_FromString("C-embedding");
> > pModule2 = PyImport_Import(pName2);
> > pFunc2 = PyObject_GetAttrString(pModule2,"buff");
>
> Get?? Do you want Set? Is buff a Python function? Or is it the
> destination of the "sending"? Any good reason for not checking the
> return value for an error? [Rhetorical question; answer == "No"]
>
> > pValue2 = PyObject_CallObject(pFunc2,pValue);
>
> CallObject?? You used this before because you had a function and
> wanted to call it because it returned you a value .... now you want to
> do one of (in Python terms)
>
> value = amodule.anattr
> value = getattr(amodule, "anattr")
>
> or
>
> amodule.anattr = value
> setattr(amodule, "anattr", value)
>
> > pValue2 is now False!
>
> False?? Do you mean the C NULL?
>
> > So i guess i cannot pass pValue as an argument
> > to PyObject_CallObject when i want to pass an python list as an
> > argument. But how must a go about to make this work?
>
> It's mainly just a matter of (1) knowing what you want to do (2)
> picking the API that does what you want (3) checking the returned
> value for error after every call.
>
> HTH,
> John

I tried to keep this simple, but I realise that since I'm not using
the terminology correctly, it may be hard understand what I mean.

I'll do something even simpler:

Say you have the function:

C-embedding.buff

def buff(s):
	if isinstance(s,list):
           return s

how can i call (use,invoke,?? - sorry, about the terminology again)
this function from C so that I call this function with an argument
that is (accepted as) a python list?

foo.bar

def bar():


pName = PyString_FromString("foo");
pModule = PyImport_Import(pName);
pFunc = PyObject_GetAttrString(pModule,"bar");
pValue = PyObject_CallObject(pFunc,NULL);