High performance mass short string search in Python

Question

The Problem: A large static list of strings is provided as A, A long string is provided as B, strings in A are all very short (a keywords

Answer 1

Depending on how long your long string is, it may be worth it to do something like this:

ls = 'my long string of stuff'
#Generate all possible substrings of ls, keeping only uniques
x = set([ls[p:y] for p in range(0, len(ls)+1) for y in range(p+1, len(ls)+1)])

result = []
for word in A:
    if word in x:
        result.append(word)

Obviously if your long string is very, very long then this also becomes too slow, but it should be faster for any string under a few hundred characters.