How to generate permutations of a list without “reverse duplicates” in Python using generators

Question

This is related to question How to generate all permutations of a list in Python

How to generate all permutations that match following criteria: if

Answer 1

How about this:

from itertools import permutations

def rev_generator(plist):
    reversed_elements = set()
    for i in permutations(plist):
        if i not in reversed_elements:
            reversed_i = tuple(reversed(i))
            reversed_elements.add(reversed_i)
            yield i

>>> list(rev_generator([1,2,3]))
[(1, 2, 3), (1, 3, 2), (2, 1, 3)]

Also, if the return value must be a list, you could just change the yield i to yield list(i), but for iteration purposes, the tuples will work just fine.