Efficient Way of making a set of tuple in which the order of tuple doesn't matters

Question

I want to make a set of tuples in which the order of tuples shouldn't matter. For eg.- If the tuples I want to add is :

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

It should output like this:

{(1,2),(1,3)}

Is there any efficient way of doing this in python?

Answer 1

You can apply sorted and then tuple, followed by conversion to set:

res = set(map(tuple, map(sorted, L)))

print(res)

{(1, 2), (1, 3)}

Explanation

There are a couple of good reasons why you should not convert each tuple to set as an initial step:

1. Tuples (1, 1, 2) and (1, 2) would become equal after conversion to set.
2. Even in the case where we are considering tuples of length 2, we would be adding an assumption that tuple({(1, 2)}) and tuple({(2, 1)}) are equal. While this may be true, it would be considered an implementation detail, since set is considered to be unordered.

Function composition

Function composition is not native to Python, but if you have access to the 3rd party toolz library you can avoid nested map:

from toolz import compose

tup_sort = compose(tuple, sorted)

res = set(map(tup_sort, L))