What is the cleanest way to do a sort plus uniq on a Python list?

Question

Consider a Python list my_list containing [\'foo\', \'foo\', \'bar\'].

What is the most Pythonic way to uniquify and sort a list ?
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Answer 1

# Python ≥ 2.4
# because of (generator expression) and itertools.groupby, sorted

import itertools

def sort_uniq(sequence):
    return (x[0] for x in itertools.groupby(sorted(sequence)))

Faster:

import itertools, operator
import sys

if sys.hexversion < 0x03000000:
    mapper= itertools.imap # 2.4 ≤ Python < 3
else:
    mapper= map # Python ≥ 3

def sort_uniq(sequence):
    return mapper(
        operator.itemgetter(0),
        itertools.groupby(sorted(sequence)))

Both versions return an generator, so you might want to supply the result to the list type:

sequence= list(sort_uniq(sequence))

Note that this will work with non-hashable items too:

>>> list(sort_uniq([[0],[1],[0]]))
[[0], [1]]