Set of lists

lists = set([ [2, 3], [1, 2] ])

Output:

Traceback (most recent call last):
  File "/home/gabor/work/slides/python/examples/sets/set_of_lists.py", line 1, in <module>
    lists = set([ [2, 3], [1, 2] ])
TypeError: unhashable type: 'list'