On 22/03/2020 19:59, Steve Jorgensen wrote:
Currently, the `issubset` and `issuperset` methods of set objects accept arbitrary
iterables as arguments. An iterable that is both a subset and superset is, in a sense,
"equal" to the set. It would be inappropriate for `==` to return `True` for
such a comparison, however, since that would break the `Hashable` contract.
Should sets have an additional method, something like `like(other)`, `issimilar(other)`, or
`isequivalent(other)`, that returns `True` for any iterable that contains the all of the items in
the set and no items that are not in the set? It would therefore be true in the same cases where
`<set> = set(other)` or `<set>.issubset(other) and <set>.issuperset(other)` is
true.
You worded the above carefully, but it may not be universally obvious that
<set>.isequivalent(other) == True
does not imply
len(<set>) == len(other)
(assuming `other` has a len() method), e.g.
<set> = set("a")
other = list("aa")
I think this point should be documented, lest someone interpret
`isequivalent` as "equals".
A similar point holds with the existing `issuperset` method (a set can
be shorter than something it is a superset of),
but I think there would be more danger of confusion with this new method.
+0 on the proposal
Rob Cliffe
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