python - How to get combinations of elements from a list?

Question

I have a list L = [1,2,3]. What's the best way to get all the possible unique combinations of 2 elements from the list and output should get in iterative way like:

1st iter = 1 2, 2nd iter = 1 3 and 3rd iter = 2 3

Answer 1

The best way is to use the itertools.combinations, like this

from itertools import combinations
print [item for item in combinations(L, r = 2)]
# [(1, 2), (1, 3), (2, 3)]

You can iterate over that like this

for item in combinations(L, r = 2):
    print item
# (1, 2)
# (1, 3)
# (2, 3)

Or you can access the individual elements like this

for item in combinations(L, r = 2):
    print item[0], item[1]