Groups > comp.lang.python > #197778

Re: Coming In Python 3.15: Sentinel Values

From	Jon Ribbens <jon+usenet@unequivocal.eu>
Newsgroups	comp.lang.python
Subject	Re: Coming In Python 3.15: Sentinel Values
Date	2026-05-11 07:13 +0000
Organization	A noiseless patient Spider
Message-ID	<slrn11030c6.425.jon+usenet@raven.unequivocal.eu> (permalink)
References	<10tr770$omms$1@dont-email.me> <87qznibnnn.fsf@nightsong.com> <10trsmv$tabj$3@dont-email.me>

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On 2026-05-11, Lawrence D’Oliveiro <ldo@nz.invalid> wrote:
> On Sun, 10 May 2026 21:01:00 -0700, Paul Rubin wrote:
>> Lawrence D’Oliveiro <ldo@nz.invalid> writes:
>>> For those times when a simple “None” marker element is not
>>> sufficient, this will be very convenient.
>>
>> object() has always worked for me.
>
> I have done the same, on a few occasions. That’s been a common idiom
> among Python programmers since practically forever. The PEP discusses
> why this is less than an optimal solution: less-than-explanatory
> diagnostics, and difficulty with type signatures for static typing.

I've always used (and seen) "SENTINEL = []"...

> Also, an “is” comparison fails if you should (inadvertently or
> otherwise) make a copy of your sentinel object.

That doesn't seem terribly likely to happen by accident though.

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Thread

Coming In Python 3.15: Sentinel Values Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-05-11 00:17 +0000
  Re: Coming In Python 3.15: Sentinel Values Paul Rubin <no.email@nospam.invalid> - 2026-05-10 21:01 -0700
    Re: Coming In Python 3.15: Sentinel Values Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-05-11 06:24 +0000
      Re: Coming In Python 3.15: Sentinel Values Jon Ribbens <jon+usenet@unequivocal.eu> - 2026-05-11 07:13 +0000
  Re: Coming In Python 3.15: Sentinel Values Tim Daneliuk <info@tundraware.com> - 2026-05-11 19:51 -0500
    Re: Coming In Python 3.15: Sentinel Values Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-05-12 02:42 +0000
      Re: Coming In Python 3.15: Sentinel Values Tim Daneliuk <info@tundraware.com> - 2026-05-12 09:52 -0500
    Re: Coming In Python 3.15: Sentinel Values Paul Rubin <no.email@nospam.invalid> - 2026-05-12 01:03 -0700
      Re: Coming In Python 3.15: Sentinel Values Tim Daneliuk <info@tundraware.com> - 2026-05-12 09:54 -0500

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