[Python-Dev] Arbitrary attributes on funcs and methods

[Greg Stein]

On Mon, 10 Apr 2000 bwarsaw@python.org wrote:
>...
> >...
> > + 	rtn = PyMember_Get((char *)im, instancemethod_memberlist, name);
> > + 	if (rtn == NULL) {
> > + 		PyErr_Clear();
> > + 		rtn = PyObject_GetAttrString(im->im_func, name);
> > + 		if (rtn == NULL)
> > + 			PyErr_SetString(PyExc_AttributeError, name);
> 
>     GS> Why do you mask this second error with the AttributeError?
>     GS> Seems that you should just leave whatever is there (typically
>     GS> an AttributeError, but maybe not!).
> 
> Good point here, but...
> 
> > + 	rtn = PyMember_Get((char *)op, func_memberlist, name);
> > + 	if (rtn == NULL) {
> > + 		PyErr_Clear();
> > + 		rtn = PyDict_GetItemString(op->func_dict, name);
> > + 		if (rtn == NULL)
> > + 			PyErr_SetString(PyExc_AttributeError, name);
> 
>     GS> Again, with the masking...
> 
> ...here I don't want the KeyError to leak through the getattr() call.

Ah! Subtle difference in the code there :-)

I agree with you, on remapping the second one. I don't think the first
needs to be remapped, however.

> If you do "print func.non_existent_attr" wouldn't you want an
> AttributeError instead of a KeyError?  Maybe it should explicitly test
> for KeyError rather than masking any error coming back from
> PyDict_GetItemString()?  Or better yet (based on your suggestion
> below), it should do a PyMapping_HasKey() test, raise an
> AttributeError if not, then just return PyMapping_GetItemString().

Seems that you could just do the PyMapping_GetItemString() and remap the
error *if* it occurs. Presumably, the exception is the infrequent case and
can stand to be a bit slower.

Cheers,
-g

-- 
Greg Stein, http://www.lyra.org/