> On 18 Mar 2022, at 14:37, Joao S. O. Bueno <jsbu...@python.org.br> wrote:
Please don’t toppost when responding to a normally threaded message. That makes it unnecessary hard to follow the conversation. > > IMO this is a purism that have little, if any place in language restrictions. > I see that not allowing. "run once" iterables could indeed void attempts to > write > "deliberatly non cooperative code" - but can it even be reliably detected? > > The other changes seem just to break backwards compatibility for little or no > gain at all. It may not be worth the trouble to fix this, but Serhiy’s proposal does try to fix a ward. It may be better to rely on linter’s here, but one way to do this with few backward compatibility concerns: - if __slots__ is a dict keep it as is - Otherwise use tuple(__slots__) while constructing the class and store that value in the __slots__ attribute of the class That way the value of the attribute reflects the slots that were created while not breaking code that uses __slots__ and doesn’t change the value after class creation. Ronald > > > > On Fri, Mar 18, 2022 at 6:57 AM Ronald Oussoren via Python-Dev > <python-dev@python.org <mailto:python-dev@python.org>> wrote: > > >> On 18 Mar 2022, at 10:29, Serhiy Storchaka <storch...@gmail.com >> <mailto:storch...@gmail.com>> wrote: >> >> Currently __slots__ can be either string or an iterable of strings. >> >> 1. If it is a string, it is a name of a single slot. Third-party code which >> iterates __slots__ will be confused. >> >> 2. If it is an iterable, it should emit names of slots. Note that >> non-reiterable iterators are accepted too, but it causes weird bugs if >> __slots__ is iterated more than once. For example it breaks default pickling >> and copying. >> >> I propose to restrict the type of __slots__. Require it always been a tuple >> of strings. Most __slots__ in real code are tuples. It is rarely we need >> only single slot and set __slots__ as a string. >> >> It will break some code (there are 2 occurrences in the stdlib an 1 in >> scripts), but that code can be easily fixed. > > Pydoc supports __slots__ that is a dict, and will use the values in the dict > als documentation for the slots. I’ve also seen code using ``__slots__ = > “field1 field2”.split()``. I don’t particularly like this code pattern, but > your proposal would break this. > > Also note that __slots__ only has a side effect during class definition, > changing it afterwards is possible but has no effect (“class Foo: pass; > Foo.__slots__ = 42”). This surprised my recently and I have no idea if this > feature is ever used. > > Ronald > >> >> _______________________________________________ >> Python-Dev mailing list -- python-dev@python.org >> <mailto:python-dev@python.org> >> To unsubscribe send an email to python-dev-le...@python.org >> <mailto:python-dev-le...@python.org> >> https://mail.python.org/mailman3/lists/python-dev.python.org/ >> <https://mail.python.org/mailman3/lists/python-dev.python.org/> >> Message archived at >> https://mail.python.org/archives/list/python-dev@python.org/message/E32BRLAWOU5GESMZ5MLAOIYPXSL37HOI/ >> >> <https://mail.python.org/archives/list/python-dev@python.org/message/E32BRLAWOU5GESMZ5MLAOIYPXSL37HOI/> >> Code of Conduct: http://python.org/psf/codeofconduct/ >> <http://python.org/psf/codeofconduct/> > > — > > Twitter / micro.blog: @ronaldoussoren > Blog: https://blog.ronaldoussoren.net/ <https://blog.ronaldoussoren.net/> > _______________________________________________ > Python-Dev mailing list -- python-dev@python.org > <mailto:python-dev@python.org> > To unsubscribe send an email to python-dev-le...@python.org > <mailto:python-dev-le...@python.org> > https://mail.python.org/mailman3/lists/python-dev.python.org/ > <https://mail.python.org/mailman3/lists/python-dev.python.org/> > Message archived at > https://mail.python.org/archives/list/python-dev@python.org/message/YQUWR7CYKNM65HR5FZQ3BANR5SNNK6N6/ > > <https://mail.python.org/archives/list/python-dev@python.org/message/YQUWR7CYKNM65HR5FZQ3BANR5SNNK6N6/> > Code of Conduct: http://python.org/psf/codeofconduct/ > <http://python.org/psf/codeofconduct/> — Twitter / micro.blog: @ronaldoussoren Blog: https://blog.ronaldoussoren.net/
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