bpo-38328: Speed up the creation time of constant list and set literals. by brandtbucher · Pull Request #17114 · python/cpython

$ python3 -m timeit -s "a=frozenset((1,2))" -- "{*a}"
5000000 loops, best of 5: 63.4 nsec per loop
$ python3 -m timeit "{1,2}"
5000000 loops, best of 5: 61.5 nsec per loop

$ python3 -m timeit "[*(1,2)]"
5000000 loops, best of 5: 46.5 nsec per loop
$ python3 -m timeit "[1,2]"
5000000 loops, best of 5: 46.6 nsec per loop