Commutative combination of elements of two lists

Question

Just a style question: Is there a build-in method to get the combinations under the assertion of commutative property and excluding elements paired with itself?

Answer 1

Assuming a and b are identical.

>>> import itertools
>>> a = ["1", "2", "3"]
>>> list(itertools.combinations(a,2))
[('1', '2'), ('1', '3'), ('2', '3')]