Get unique combinations of elements from a python list

python list combinations
Allen picture Allen · Aug 13, 2013 · Viewed 48.8k times · Source

Edit: This is not a exact duplicate of How to get all possible combinations of a list’s elements?

This topic is about finding unique combinations while the other topic is about finding ALL combinations.

If I have a python list:

 L = [1,2,3,4]

what's the best way to get all the possible unique combinations of 3 elements from the list like below:

["1,2,3", "1,2,4", "2,3,4", "3,4,1"]

The order of the elements in the combinations doesn't matter. For example, "1,2,3" and "3,2,1" will be considered the same combination.

I can probably write a few loops to do this but I think there might be a one-liner which can do the same.

Answer

Ashwini Chaudhary picture Ashwini Chaudhary · Aug 13, 2013

You need itertools.combinations:

>>> from itertools import combinations
>>> L = [1, 2, 3, 4]
>>> [",".join(map(str, comb)) for comb in combinations(L, 3)]
['1,2,3', '1,2,4', '1,3,4', '2,3,4']

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