Sorry, minor bug in the example implementation:
def sentinel(name):
cls = type(name, (), {
'__repr__': lambda self: f"<{self.__class__.__name__}>",
'__copy__': lambda self: self,
'__deepcopy__': lambda self, memo: self,
})
return cls()
> Tim Hoffmann hat am 31
The standard pattern to create a sentinel in Python is
>>> Unset = object()
While this is often good enough, it has some shortcomings:
- repr(Unset) is unhelpful:
- copy/deepcopy create a copy of the sentinel object, which can lead to
surprising results such as:
>>> d = {'val': Unset}
On Thu, 31 Aug 2023 at 18:55, Tim Hoffmann via Python-ideas
wrote:
>
> The standard pattern to create a sentinel in Python is
>
> >>> Unset = object()
>
> While this is often good enough, it has some shortcomings:
>
> - repr(Unset) is unhelpful:
>
Looks like you may be thinking of this:
https:/
Seems nice. Just write a library and upload it to one of the usual places?
On Thu, 31 Aug 2023, 16:54 Tim Hoffmann via Python-ideas, <
python-ideas@python.org> wrote:
> The standard pattern to create a sentinel in Python is
>
> >>> Unset = object()
>
> While this is often good enough, it has some
There is already
https://pypi.org/project/sentinel/
https://pypi.org/project/sentinels/
Though, I think this should become part of the standard library. It's a
fundamental concept, somewhat analogous to namedtuples, enums and dataclass
(only a bit less used, but also less complex). Once figur
