Shivkumar - 1 year ago 67
Python Question

# How to get single unique permutation entry from list

I have this list after permutation:

``````import itertools
print list(itertools.permutations([1,2,3,4], 2))
``````

Here's the output :

[(1, 2), (1, 3), (1, 4),
(2, 1), (2, 3), (2, 4), (3, 1), (3, 2), (3, 4), (4, 1), (4, 2), (4, 3)]

In that list we can find replicated elements like (1,2) - (2,1) and (1,3) - (3,1) and so ..

What I want is to get only one replicate element from this list, output list like:

``````[(1, 2),(1, 3),(1, 4),(2, 3),(2, 4),(3, 4)]
``````

You need the combinations of the list, and not the permutations. For that there is `itertools.combinations()` function in Python:

``````>>> from itertools import combinations
>>> l = [1,2,3,4]
>>> list(combinations(l, 2))
[(1, 2), (1, 3), (1, 4), (2, 3), (2, 4), (3, 4)]
``````

As per the document:

• Permutations are for lists (order matters)

• Combinations are for groups (order doesnâ€™t matter).

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