how to remove 50000 elements from a 100000 list?

[Sion Arrowsmith]

Tim Chase  <python.list at tim.thechases.com> wrote:
>Another attempt might be to try
>
> >>> a = [x for x in a if x not in b]
>
>However, this is still doing A*B checks, and will likely 
>degrade with as their sizes increase.

Combine this with the use of sets others have suggested if the
order of a matters, ie:

>>> bset = set(b)
>>> a = [ x for x in a if x not in bset ]

which gets you down to O(A) since set membership is O(1).

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