On Fri, 15 Dec 2017 14:05:46 +0200 Serhiy Storchaka <storch...@gmail.com> wrote: > 15.12.17 04:00, Guido van Rossum пише: > > In the light of Antoine's and Stephan's feedback I think this can be > > reconsidered -- while I want to take a cautious stance about resource > > consumption I don't want to stand in the way of progress. > > I don't see any problems with implementing this on types defined in C. > This isn't harder than implementing __sizeof__ or pickling support, and > NumPy classes already have implemented both. Maybe Yury forgot about > METH_STATIC and METH_CLASS? > > The cost of adding new slots: > > 1. Increased memory consumption. This increases the size of *every* > class, even if they don't implement this feature. > > 2. Increased class initialization time. For every class for every slot > we need to look up corresponding methods in dictionaries of the class > itself and all its parents (caching doesn't work fine at this stage). > Significant part of class initialization time is spent on initializing > slots. This will increase the startup time and the time of creating > local classes. The relative overhead is more significant in Cython. > > 3. We need to add a new type feature flag Py_TPFLAGS_HAVE_*. The number > of possible flags is limited, and most bits already are used. We can add > the limited number of new slots, and should not spent this resource > without large need. > > 4. Increased complexity. Currently the code related to PEP 560 is > located in few places. With supporting new slots we will need to touch > more delicate code not related directly to PEP 560. It is hard to review > and to test such kind of changes. I can't guarantee the correctness.
These are all very good points (except #1 which I think is a red herring, see my posted example). Do you have any general idea how to speed up class creation? Regards Antoine. _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
