$ python2 -c "import timeit; print timeit.timeit('d.viewkeys() & b', setup='import random; a=set(random.sample(range(10000000), 1000000)); b=set(random.sample(range(10000000), 1000000)); d={i:i for i in a}', number=10)"
2.20387506485
$ python2 -c "import timeit; print timeit.timeit('d.viewkeys() & b', setup='import random; a=set(random.sample(range(10000000), 1000000)); b=set(random.sample(range(10000000), 1000000)); d={i:i for i in a}', number=10)"
2.14592909813
$ python2 -c "import timeit; print timeit.timeit('d.viewkeys() & b', setup='import random; a=set(random.sample(range(10000000), 1000000)); b=set(random.sample(range(10000000), 1000000)); d={i:i for i in a}', number=10)"
2.11002802849
$ python2 -c "import timeit; print timeit.timeit('set(d) & b', setup='import random; a=set(random.sample(range(10000000), 1000000)); b=set(random.sample(range(10000000), 1000000)); d={i:i for i in a}', number=10)"
1.4978749752
$ python2 -c "import timeit; print timeit.timeit('set(d) & b', setup='import random; a=set(random.sample(range(10000000), 1000000)); b=set(random.sample(range(10000000), 1000000)); d={i:i for i in a}', number=10)"
1.50220894814
$ python2 -c "import timeit; print timeit.timeit('set(d) & b', setup='import random; a=set(random.sample(range(10000000), 1000000)); b=set(random.sample(range(10000000), 1000000)); d={i:i for i in a}', number=10)"
1.49954104424