python - Remove sublist duplicates including reversed

Question

For example i have following

list = [['1', '2'], ['1', '3'], ['1', '4'], ['1', '5'], ['2', '1'], ['4', '1'], ['2', '6']]

I want to match if a sub list has a reversed sub list within same list (i.e. ['1', '2'] = ['2', '1']) , and if True than to remove from the list the mirrored one.

The final list should look like :

list = [['1', '2'], ['1', '3'], ['1', '4'], ['1', '5']['2', '6']]

This is what i tried:

for i in range(len(list)):
    if list[i] == list[i][::-1]:
            print("Match found")
            del list[i][::-1]

print(list)

But finally I get the same list as original. I am not sure if my matching condition is correct.

Answer 1

You could iterate over the elements of the list, and use a set to keep track of those that have been seen so far. Using a set is a more convenient way to check for membership, since the operation has a lower complexity, and in that case you'll need to work with tuples, since lists aren't hashable. Then just keep those items if neither the actual tuple or the reversed have been seen (if you just want to ignore those which have a reversed you just need if tuple(reversed(t)) in s):

s = set()
out = []
for i in l:
    t = tuple(i)
    if t in s or tuple(reversed(t)) in s:
        continue
    s.add(t)
    out.append(i)

---

print(out)
# [['1', '2'], ['1', '3'], ['1', '4'], ['1', '5'], ['2', '6']]