python - Should I check if an item is already in a set before adding it? -


if foo builtin set know contains "bar", of these faster? more pythonic?

foo.add("bar")

or

if foo not in bar:     foo.add("bar")

actually, second may faster (output ipython):

in [2]: %timeit s.add("a") slowest run took 68.27 times longer fastest. mean intermediate result being cached  10000000 loops, best of 3: 73.3 ns per loop  in [3]: %timeit if not "a" in s: s.add("a") 10000000 loops, best of 3: 37.1 ns per loop

but anyway, the first 1 more pythonic, agree.


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