python内置类 set

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 non-membership in s.

isdisjoint(other)
Return True if the set has no elements in common with other. Sets are disjoint if and only if their intersection is the empty set.

issubset(other)
set <= other
Test whether every element in the set is in other.

set < other
Test whether the set is a proper subset of other, that is, set <= other and set != other.

issuperset(other)
set >= other
Test whether every element in other is in the set.

set > other
Test whether the set is a proper superset of other, that is, set >= other and set != other.

union(*others)
set | other | …
Return a new set with elements from the set and all others.

intersection(*others)
set & other & …
Return a new set with elements common to the set and all others.

difference(*others)
set - other - …
Return a new set with elements in the set that are not in the others.

symmetric_difference(other)
set ^ other
Return a new set with elements in either the set or other but not both.