Forgive me if this has already been discussed.
Could we add the idea of "negative" sets to Python? That means sets that
contain EVERYTHING EXCEPT certain elements.
First, let's have a universal set that contains everything.
assert element in set.UNIVERSAL
The universal set is a superset of every other set.
assert set.UNIVERSAL >= any_set
Adding anything to universal set doesn't change anything.
assert set.UNIVERSAL | element == set.UNIVERSAL
However REMOVING an element from the set puts it on "negative list".
myset = set.UNIVERSAL
myset.remove(element)
assert element not in myset
Intersection of a "negative set" with a normal set gives again a normal
set. Union of two negative sets, or a negative set with a normal set,
gives a negative set.
The main issue: negative sets would not be iterable, but you can
intersect them with the desired subdomain and iterate over.
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