Actually, in Python 2.7 and 3.2+, this really does work:
>>> b = {"foo", "bar"}
>>> b
set(['foo', 'bar'])
You can’t use [] access on a set (“key into”), but you can test for inclusion:
>>> 'x' in b
False
>>> 'foo' in b
True
Sets are as close to value-less dictionaries as it gets. They have average-case constant-time access, require hashable objects (i.e. no storing lists or dicts in sets), and even support their own comprehension syntax:
{x**2 for x in xrange(100)}