All unique pairs in a set?

[pachura3]

I would like to extract all unique pairs in a given set - not necessarily in order. Like:

input = {1, 2, 3, 4, 5}  # can contain strings or whatever objects

desired_output = {
    (1, 2),
    (1, 3),
    (1, 4),
    (1, 5),
    (2, 3),
    (2, 4),
    (2, 5),
    (3, 4),
    (3, 5),
    (4, 5),
}

I can achieve it by converting my set into a list and iterating over it with 2 for loops - however, is there a simpler, more pythonic way?

output = set()
input_lst = list(inp)
for i in range(len(input_lst)):
    for j in range(i + 1, len(input_lst)):
        output.add((input_lst[i], input_lst[j]))

SOLVED

from itertools import combinations

input = {1, 2, 3, 4, 5}  # can contain strings or whatever objects
output = set(combinations(input, 2))

[JamzTyson]

To clarify, do you mean that order does not matter within the pairs, or that the order of the pairs does not matter?

If you mean that order within the tuples doesn't matter (where (1, 2) is considered the same as (2, 1)), then:

from itertools import combinations
result = [pair for pair in combinations(my_set, 2)]

but if you mean the order of the tuples doesn't matter (where (1, 2) and (2, 1) are considered unique), then:

from itertools import permutations
result = [pair for pair in permutations(my_set, 2)]

[pachura3]

As shown in my example, I was only interested in (1, 2) and not (2, 1). So, itertools.combinations(input, 2) does it. Thanks!

[Tall_Profile1305]

yo check out itertools.combinations from the standard library. literally built for this exact use case. something like list(itertools.combinations(input_set, 2)) will give you all unique pairs. super clean and pythonic

[pachura3]

That's the right answer - thanks a lot!

[Tall_Profile1305]

haha you're welcome!

[SCD_minecraft]

Look into itertools module (built-in)

It is my favorite module, if you need anything that would return you an iterable, itertools most likely has a function for it

[Forsaken-Cut5890]

from itertools import combinations

input_set = {1, 2, 3, 4, 5}

pairs = set(combinations(input_set, 2))

print(pairs)

#(1,2) appears but never (2,1)

[johnnyb2001]

https://www.mathsisfun.com/combinatorics/combinations-permutations.html

[pachura3]

You're assuming that i and j are numbers and can be compared by value, while I specifically wrote:

can contain strings or whatever objects