Running across a subset of a list in python -

is possible run through subset in python list?

i have following problem, have 2 lists, list1 long , list2 quite short. now, want check elements of list2 in list1. current version looks this:

for item in list1:     if item in list2:         # 

this takes long time. possible subset , run through list?

i need many times.

if list elements hashable, can find intersection using sets:

>>> x in set(list2).intersection(list1):         print x 

if not hashable, can @ least speed-up search sorting shorter list , doing bisected lookups:

>>> bisect import bisect_left >>> list2.sort() >>> n = len(list2) >>> x in list1:         = bisect_left(list2, x)         if != n , list2[i] == x:             print x 

if data elements neither hashable nor sortable, won't able speed-up original code:

>>> x in list1:         if x in list2:             print x 

the running time of set-intersection approach proportional sum of lengths of 2 lists, o(n1 + n2). running time of bisected-search approach o((n1 + n2) * log(n2)). running time of original brute-force approach o(n1 * n2).