On 2 February 2012 21:38, Dag Sverre Seljebotn <d.s.seljeb...@astro.uio.no> wrote: > On 02/02/2012 10:16 PM, mark florisson wrote: >> >> On 2 February 2012 12:19, Dag Sverre Seljebotn >> <d.s.seljeb...@astro.uio.no> wrote: >>> >>> I just realized that >>> >>> cdef int[:] a = None >>> >>> raises an exception; even though I'd argue that 'a' is of the "reference" >>> kind of type where Cython usually allow None (i.e., "cdef MyClass b = >>> None" >>> is allowed even if type(None) is NoneType). Is this a bug or not, and is >>> it >>> possible to do something about it? >>> >>> Dag Sverre >>> _______________________________________________ >>> cython-devel mailing list >>> cython-devel@python.org >>> http://mail.python.org/mailman/listinfo/cython-devel >> >> >> Yeah I disabled that quite early. It was supposed to be working but >> gave a lot of trouble in cases (segfaults, mainly). At the time I was >> trying to get rid of all the segfaults and get the basic functionality >> working, so I disabled it. Personally, I have never liked how things > > > Well, you can segfault quite easily with > > cdef MyClass a = None > print a.field > > so it doesn't make sense to slices different from cdef classes IMO. > > >> can be None unchecked. I personally prefer to write >> >> cdef foo(obj=None): >> cdef int[:] a >> if obj is None: >> obj = ... >> a = obj >> >> Often you forget to write 'not None' when declaring the parameter (and >> apparently that it only allowed for 'def' functions). >> >> As such, I never bothered to re-enable it. However, it does support >> control flow with uninitialized slices, and will raise an error if it >> is uninitialized. Do we want this behaviour (e.g. for consistency)? > > > When in doubt, go for consistency. So +1 for that reason. I do believe that > setting stuff to None is rather vital in Python.
Yeah I think we should go back to this discussion :) Checking for None and allowing slices to be None is simply very convenient, and doesn't involve any drastic changes. I was never really against it, I just never got around to implementing it. > What I typically do is more like this: > > def f(double[:] input, double[:] out=None): > if out is None: > out = np.empty_like(input) > ... > > Having to use another variable name is a bit of a pain. (Come on -- do you > use "a" in real code? What do you actually call "the other obj"? I sometimes > end up with "out_" and so on, but it creates smelly code quite quickly.) > > It's easy to segfault with cdef classes anyway, so decent nonechecking > should be implemented at some point, and then memoryviews would use the same > mechanisms. Java has decent null-checking... > > > Dag Sverre > _______________________________________________ > cython-devel mailing list > cython-devel@python.org > http://mail.python.org/mailman/listinfo/cython-devel _______________________________________________ cython-devel mailing list cython-devel@python.org http://mail.python.org/mailman/listinfo/cython-devel
