A fast way to find the number of elements in list intersection (Python)

Question

Is there any faster way to calculate this value in Python:

len([x for x in my_list if x in other_list])

I tried to use sets, since the lists' elements are unique, but I noticed no difference.

len(set(my_list).intersection(set(other_list)))

I'm working with big lists, so even the slightest improvement counts. Thanks

Answer 1

I think a generator expression like so would be fast

sum(1 for i in my_list if i in other_list)

Otherwise a set intersection is about as fast as it will get

len(set(my_list).intersection(other_list))

Answer 2

Simple way is to find the least length'd list... than use that with set.intersection..., eg:

a = range(100)
b = range(50)

fst, snd = (a, b) if len(a) < len(b) else (b, a)
len(set(fst).intersection(snd))