fast way to filter a set?
Skip Montanaro
skip at pobox.com
Wed Sep 17 12:24:07 EDT 2003
fortepianissimo> I know I can do things like
fortepianissimo> s=Set(range(1,11))
fortepianissimo> s=Set(filter(lambda x:x%2==0,s))
fortepianissimo> But this seems a bit slow since filter returns a list
fortepianissimo> which then must be converted back to a set. Any tips?
The only thing which comes to mind is:
>>> s = sets.Set(range(1,11))
>>> s
Set([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])
>>> keys = list(s)
>>> dummy = [s.discard(x) for x in keys if x%2]
>>> s
Set([2, 4, 6, 8, 10])
You still create a list, but don't create a second set.
Skip
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