On 5/13/2021 1:39 PM, Tal Einat wrote:
On Thu, May 13, 2021 at 7:44 PM Ethan Furman <et...@stoneleaf.us> wrote:
Consider me complaining. ;-)
+1
An actual Sentinel class would be helpful:
>>> class Sentinel:
... def __init__(self, repr):
... self.repr = repr
... def __repr__(self):
... return self.repr
...
>>> MISSING = Sentinel('MISSING')
>>> MISSING
MISSING
>>> implicit = Sentinel('<implicit>')
>>> implicit
<implicit>
Here is my suggestion (also posted on the related bpo-44123), which is
also simple, ensures a single instance is used, even considering
multi-threading and pickling, and has a better repr:
class Sentinel:
def __new__(cls, *args, **kwargs):
raise TypeError(f'{cls.__qualname__} cannot be instantiated')
class MISSING(Sentinel):
pass
>>> MISSING
<class '__main__.MISSING'>
I think a repr of just "MISSING", or maybe "dataclasses.MISSING" would
be better.
Eric
_______________________________________________
Python-Dev mailing list -- python-dev@python.org
To unsubscribe send an email to python-dev-le...@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/EQZV3KZZQNBN6NQRIERUK5HOEAUW2DUJ/
Code of Conduct: http://python.org/psf/codeofconduct/
