Since the subject is this,
I will note that past week, I resorted twice to create an Enum with a
single element,
and then alias the element on the module namespace, so that it would work
as a "polished" sentinel.
So:
import enum
class Whatever(enum.Enum):
EMPTY = "EMPTY"
EMPTY = Whatever.EMPTY
A "repeat yourself three times" - certainly not that nice.
But its use was a bit off the ones listed here in a sense these
are meant to be explicitly passed to some methods (rather,
placed inside data structures) to indicate a desired behavior.
On Fri, 14 May 2021 at 21:03, Nick Coghlan <[email protected]> wrote:
> On Sat, 15 May 2021, 5:39 am Tal Einat, <[email protected]> wrote:
>
> (snip useful feature summary)
>
> The common `SENTINEL = object()` idiom fails #3, #4 and #5. This is
>> what I've been using for years, and I now think that it isn't good
>> enough. This not having a nice repr is what started this thread.
>>
>> I'd also personally prefer something simple, ideally without a new
>> class or module.
>>
>
> The key advantage of a new base class is that it offers a way to
> communicate a shift in the recommended development idiom. "sentinel =
> object()" is entrenched enough that I would expect that only a
> "types.Sentinel" base class would stand a good chance of displacing it.
>
> Why the "types" module? I don't think this is important enough to be a
> builtin type, and the types module is cheap to import, doesn't bring in
> many transitive dependencies, and the purpose of the new base class would
> be defining custom sentinel types with various desirable properties.
>
> Cheers,
> Nick.
>
>>
>
>
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