permutations with unique values

Question

itertools.permutations generates where its elements are treated as unique based on their position, not on their value. So basically I want to avoid duplicates like this:

Answer 1

This relies on the implementation detail that any permutation of a sorted iterable are in sorted order unless they are duplicates of prior permutations.

from itertools import permutations

def unique_permutations(iterable, r=None):
    previous = tuple()
    for p in permutations(sorted(iterable), r):
        if p > previous:
            previous = p
            yield p

for p in unique_permutations('cabcab', 2):
    print p

gives

('a', 'a')
('a', 'b')
('a', 'c')
('b', 'a')
('b', 'b')
('b', 'c')
('c', 'a')
('c', 'b')
('c', 'c')