从排列中清除元组列表

Question

I have a list of tuples that I generated thus:

frequencies = [(a, b, 40) for a in [x for x in range(20, 110, 10) if x != 90] for b in range(20, 90, 10)]\
+[(a, b, 40) for a in [x for x in range(20, 110, 10) if x != 90] for b in range(100, 175, 25)]\
+[(a, b, 40) for a in [x for x in range(20, 110, 10) if x != 90] for b in range(200, 400, 50)]

I would like to consider permutations sa (20, 60, 40) and (60, 20, 40) identical and so to keep only one of them.

My current approach is:

# Clean permutations
frequencies2 = list()
for f in frequencies:
    possible = list(itertools.permutations(f))
    if len([p for p in possible if p in frequencies2]) == 0:
        frequencies2.append(f)

frequencies = frequencies2

I am quite sure there is a better way to do this, but I can't find it. Although this code isn't really aesthetic, it is only O(n²).

Thanks for your help.

Answer 1

If you want to filter out permutations after the generation is complete then you can simply sort the tuples and compare them:

without_permutations = list({tuple(sorted(f)): f for f in frequencies}.values())

This builds a dict in which the sorted tuples point to the original tuples. That way, later tuples will overwrite earlier permutations of themselves.