Its faster than the built in set type. Uniqueness of values isn't a
requirement. The values need to be comparable so that they can be sorted. This
allows a linear time complexity. That's basically the only restraint on the
values. Here are some speed test results and pseudocode.
def naive(a,b):
res = [x for x in a if x not in b]
def set_test(a,b):
aset = set(a)
bset = set(b)
res = aset - bset
res= list(res)
For A not in B:
trying A 10000 elements B 50000 elements
naive test 10.285029 s
set test 0.008001 s
listex test 0.004000 s
For A subset of B:
trying A 100000 elements B 500000 elements
naive too long to wait :-)
set test 0.125013 s
listex test 0.054005s
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