class set([iterable])
class frozenset([iterable])
Return a new set or frozenset object whose elements are taken from iterable. The elements of a set must be hashable. To represent sets of sets, the inner sets must be frozenset objects. If iterable is not specified, a new empty set is returned.
Instances of set and frozenset provide the following operations:
len(s)
Return the number of elements in set s (cardinality of s).
x in s
Test x for membership in s.
x not in s
Test x for