On 11/08/2017 03:12 PM, Nathaniel Smith wrote: > - We could adjust the API so that there's some explicit operation to > trigger the final writeback. At the Python level this would probably > mean that we start supporting the use of nditer as a context manager, > and eventually start raising an error if you're in one of the "unsafe" > case and not using the context manager form. At the C level we > probably need some explicit "I'm done with this iterator now" call. > > One question is which cases exactly should produce warnings/eventually > errors. At the Python level, I guess the simplest rule would be that > if you have any write/readwrite arrays in your iterator, then you have > to use a 'with' block. At the C level, it's a little trickier, because > it's hard to tell up-front whether someone has updated their code to > call a final cleanup function, and it's hard to emit a warning/error > on something that *doesn't* happen. (You could print a warning when > the nditer object is GCed if the cleanup function wasn't called, but > you can't raise an error there.) I guess the only reasonable option is > to deprecate NPY_ITER_READWRITE and NP_ITER_WRITEONLY, and make people > switch to passing new flags that have the same semantics but also > promise that the user has updated their code to call the new cleanup > function. Seems reasonable.
When people use the Nditer C-api, they (almost?) always call NpyIter_Dealloc when they're done. Maybe that's a place to put a warning for C-api users. I think you can emit a warning there since that function calls the GC, not the other way around. It looks like you've already discussed the possibilities of putting things in NpyIter_Dealloc though, and it could be tricky, but if we only need a warning maybe there's a way. https://github.com/numpy/numpy/pull/9269/files/6dc0c65e4b2ea67688d6b617da3a175cd603fc18#r127707149 Allan _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@python.org https://mail.python.org/mailman/listinfo/numpy-discussion
