Python: See if one set contains another entirely?
Is there a fast way to check if one set entirely contains another?
Something like:
>>>[1, 2, 3].containsAll([2, 1])
True
>>>[1, 2, 3].containsAll([3, 5, 9])
False
Solution 1:
Those are lists, but if you really mean sets you can use the issubset
method.
>>> s = set([1,2,3])
>>> t = set([1,2])
>>> t.issubset(s)
True
>>> s.issuperset(t)
True
For a list, you will not be able to do better than checking each element.
Solution 2:
For completeness: this is equivalent to issubset
(although arguably a bit less explicit/readable):
>>> set([1,2,3]) >= set([2,1])
True
>>> set([1,2,3]) >= set([3,5,9])
False
Solution 3:
You can use either set.issubset()
or set.issuperset()
(or their operator based counterparts: <=
and >=
). Note that the methods will accept any iterable as an argument, not just a set:
>>> {1, 2}.issubset([1, 2, 3])
True
>>> {1, 2, 3}.issuperset([1, 2])
True
However, if you use operators, both arguments must be sets:
>>> {1, 2} <= {1, 2, 3}
True
>>> {1, 2, 3} >= {1, 2}
True