On Sun, Jun 5, 2022, 12:08 PM MRAB <pyt...@mrabarnett.plus.com> wrote:
> On 2022-06-05 16:12, David Mertz, Ph.D. wrote:
> > This is exactly the problem solved by set difference. E.g. `{a, b, c}
> - {a, c}`.
> >
> > This operation is linear on the size of the removed set.
> >
> You don't have to use a set difference, which might matter if the order
> was important, but just make a set of the ones found:
>
> s = set(b)
>
> And then the list comprehension:
>
> [x for x in a if x not in s]
>
Sure, that's nice enough code and has the same big-O complexity. I suspect
set difference is a little faster (by a constant multiple) because it hits
C code more, but I haven't benchmarked.
The OP said the elements were from fnmatch though, which explicitly does
not promise order. So really it's just whether you like your code or this
better aesthetically:
list(set(b) - set(a))
Personally I like my (somewhat shorter) version as more clear. But YMMV.
>
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