On Wed, 27 Jul 2022 at 21:54, Mathew Elman <mathew.elman@ocado.com> wrote:
I don't see why you couldn't. I guess what they do depends if any of these have defaults? Which I think they do not in this case, right? If they were non vanilla dictionaries that had a default e.g.
class SomeDict(dict): def __getitem__(self, item=None): return super().__getitem__(item)
def __contains__(self, item=None): return super().__contains__(item)
So Undefined would trigger a default, but only if there is one?
print(b[1]) would still print Undefined because print's first argument doesn't have a default.
But print doesn't have a first argument - it accepts *args. So Undefined still counts as an argument, except when there's a default, at which point it counts as a non-argument?
a in c would be False.
That is VERY surprising behaviour. For literally any other object, that would be True. But then, it would be surprising in other ways if Undefined behaved like a normal object.
c[a] would return c[None], which would raise an error here because None isn't in the mapping
Again, very surprising, if putting a value into a mapping doesn't result in that value being in the mapping.
Again, I am not pro this idea, just answering the questions you're asking as I see them :)
Yeah. I think you're doing a great job of showing why this is a bad idea :) ChrisA