Get unique combinations of elements from a python list
Question: Edit: This is not a exact duplicate of [Python code to pick out all possible
combinations from a list?](http://stackoverflow.com/questions/464864/python-
code-to-pick-out-all-possible-combinations-from-a-list)

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: You need
[`itertools.combinations`](https://docs.python.org/2/library/itertools.html#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']
    

