I have also wanted sentinel objects many times. These are often useful for creating a "Not Specified" default value when explicitly passing `None` has semantic meaning.
There are a few issues with the `sentinel = object()` code. One is that they don't repr well so they make debugging harder. Another issue is that they cannot be pickled or copied. You also cannot take a weak reference to a sentinel which can break some caching code and makes them harder to use. At work we have a small helper to create sentinels with a name and optional doc string which is open sourced here: https://github.com/quantopian/zipline/blob/master/zipline/utils/sentinel.py. On Thu, Jul 5, 2018 at 3:44 PM, Ed Kellett <e+python-id...@kellett.im> wrote: > Hi! > > On 2018-07-05 20:38, Flavio Curella wrote: >> More than once I've found myself wanting to create a 'sentinel' value. The >> most common use case is to differentiate between an argument that has not >> been provided, and an argument provided with the value `None`. > > I generally do something like > > _nothing = object() > >> Furthermore, without a common implementation in the std library, various >> Python libraries had to write their own implementations, which all differs >> in functionality and behavior. > > What functionality does such a thing actually need? > _______________________________________________ > Python-ideas mailing list > Python-ideas@python.org > https://mail.python.org/mailman/listinfo/python-ideas > Code of Conduct: http://python.org/psf/codeofconduct/ _______________________________________________ Python-ideas mailing list Python-ideas@python.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/
