If A
and B
are sets
A - B
is everything in A
that’s not in B
.
>>> A = {1,2,3}
>>> B = {1,4,5}
>>>
>>> A - B
{2, 3}
>>> B - A
{4, 5}
A.symmetric_difference(B)
are all the elements that are in exactly one set, i.e. the union of A - B
and B - A
.
>>> A.symmetric_difference(B)
{2, 3, 4, 5}
>>> (A - B).union(B - A)
{2, 3, 4, 5}