Sorry, this got lost in the shuffle without being sent, and the
conversation seems to have died down. but since I wrote it ...
On Sat, Jul 4, 2020 at 8:25 AM Stephen J. Turnbull <
turnbull.stephen...@u.tsukuba.ac.jp> wrote:
> Christopher Barker writes:
>
> > I am really confused here -- I'm suggesting that is should NOT be
> possible
> > to tell the difference.
>
> But it is possible to tell the difference, so that suggestion is moot.
I meant in the context of putting things in, or testing whether they are
in, sets. Not in any other context.
There are languages where there is no numeric tower, just numbers, and
> [0][0], [0][0.0], and [0][0+0j] all just work. Python isn't one of
> them. Fewer places you can tell in Python 3 than in Python 2, I
> believe, but several remain.
Sure, but putting them in sets, or using them as a key in a dict is not one
of them.
set.intern does yield the same result regardless of what's passed in:
> whichever is in the set. That's *why* I can call it "intern".[1]
Fair enough. You can of course propose any functionality you want. I’m
suggesting that my understanding of what you are proposing doesn’t match
well with the rest of how sets work.
But to see if I understand correctly, you couldn’t quite use a set to
intern objects: once 2.0 was in there you could not put 2 in as well. You
could know that 2.0 was already in there when you tried to add 2, but it
would still never be added.
It seems if you really want to intern objects, you’d need something kind of
like, but not quite, a set().
Note: this all is only an issue for object that are of a different type,
but can compare equal and have the same hash - maybe the numeric types are
the only ones in the stdlib for which this is the case. Nevertheless, they
are commonly used :-)
Nope: turns out NamedTuples and Tuple are the "same" as far as sets are
concerned as well.
In [66]: s = {p}
In [67]: s
Out[67]: {Point(x=2, y=3)}
In [68]: s.add((2,3))
In [69]: s
Out[69]: {Point(x=2, y=3)}
In [70]: s = {(2,3)}
In [71]: s.add(p)
In [72]: s
Out[72]: {(2, 3)}
So if you want something that treats different types with the same value as
different, you really will need a different storage mechanism than a set.
-CHB
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