On Sat, Sep 10, 2022 at 6:58 AM Tal Einat <taleinat@gmail.com> wrote:
The sentinel objects should behave as expected by a sentinel object: When compared using the is operator, it should always be considered identical to itself but never to any other object.
The current design is that sentinels with the same name from the same module will always be identical. So for example `Sentinel("name") is Sentinel("name")` will be true.
Hmm -- so it's a semi-singleton -- i.e. behaves like a singlton, but only in a particular module namespace. I wonder if there's a way to make this a bit more clear in the PEP text -- but don't have any suggestions for edits at the moment :-( It would be nice if they could be true singletons, but that would require a python-global registry of some sort, which is, well, impossible. I would like to see a handful of common sentinels defined. Is there a plan to put a few that are useful for the stdlib in the `sentinel` module? Maybe that doesn't belong in the PEP, but I like the idea of a) every similar use in the stdlib uses the same one and b) having a standard set for third party code to use -- a bit like the built-in Exceptions. -CHB -- Christopher Barker, PhD (Chris) Python Language Consulting - Teaching - Scientific Software Development - Desktop GUI and Web Development - wxPython, numpy, scipy, Cython