Python get all Unique Pair combinations from list of elements

Question

I tried to get the all unique pair combinations from a list.

Here is what I have done so far,

import itertools

# Unique Combination Pairs for list of elements
def uniqueCombinations(list_elements):
    l = list(itertools.combinations(list_elements, 2))
    s = set(l)
    # print('actual', len(l), l)
    return list(s)

Test Case

sample = ["apple", "orange", "banana", "grapes", "mango"]
uniqueCombinations(sample)

Output

[('apple', 'banana'),
 ('orange', 'mango'),
 ('orange', 'grapes'),
 ('apple', 'grapes'),
 ('orange', 'banana'),
 ('apple', 'mango'),
 ('grapes', 'mango'),
 ('apple', 'orange'),
 ('banana', 'mango'),
 ('banana', 'grapes')]

The input will be unique strings of list. Assume that duplicate elements will not be passed.

Is there a better / more elegant / more accurate way to do this??

Answer 1

From itertools.combinations, emphasis mine:

Return r length subsequences of elements from the input iterable.

The combination tuples are emitted in lexicographic ordering according to the order of the input iterable. So, if the input iterable is sorted, the combination tuples will be produced in sorted order.

Elements are treated as unique based on their position, not on their value. So if the input elements are unique, there will be no repeat values in each combination.

Which means as long as we pass in a collection of unique elements to itertools.combinations, there will be no duplicate values in the combinations it returns. And if we can assume that the input list will not contain any duplicate elements, we can rewrite the function like so:

import itertools

def unique_combinations(elements: list[str]) -> list[tuple[str, str]]:
    """
    Precondition: `elements` does not contain duplicates.
    Postcondition: Returns unique combinations of length 2 from `elements`.

    >>> unique_combinations(["apple", "orange", "banana"])
    [("apple", "orange"), ("apple", "banana"), ("orange", "banana")]
    """
    return list(itertools.combinations(elements, 2))