Sets are containers that share properties and operations with sets in mathematics. A mathematical set is a collection of distinct objects. Here are some mathematical set expressions:
And their Python counterparts:
A = {1,2,3,4} B = {5} C = A.union(B) # returns set([1,2,3,4,5]) D = A.intersection(C) # returns set([1,2,3,4]) E = C.difference(A) # returns set([5]) 5 in C # returns True
Sets contain an element only once, corresponding to the aforementioned definition:
A = {1,2,3,3,3} B = {1,2,3} A == B # returns True
And a set is unordered; that is, the order of the elements in the set is not defined:
A = {1,2,3} B = {1,3,2} A == B # returns True
Sets in Python can contain all kinds of hashable objects, that is, numeric objects, strings, and Booleans.
There are union
and intersection
methods:
A={1,2,3,4} A.union({5}) A.intersection({2,4,6}) # returns set([2, 4])
Also, sets can be compared using the methods issubset
and issuperset
:
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