Python's sets support set arithmetic using operators.
>>> a = {1, 2, 3, 4, 7}
>>> b = {1, 3, 5, 7, 9}
Union:
>>> a | b
{1, 2, 3, 4, 5, 7, 9}
Intersection:
>>> a & b
{1, 3, 7}
Asymmetric difference:
>>> a - b
{2, 4}
Symmetric difference:
>>> a ^ b
{2, 4, 5, 9}