Here's a shorter and much faster solution: [w for w in words if set(w) <= set(puzzle) and puzzle[4] in w] Edit: Oh I see you can only use each letter once

Here's a shorter and much faster solution: [w for w in words if set(w) <= set(puzzle) and puzzle[4] in w] Edit: Oh I see you can only use each letter once. In that case you'd use a multiset here instead of set, which Python doesn't support natively unfortunately. from collections import defaultdict class bag: def __init__(self, xs): self.dict = defaultdict(int) for x in xs: self.dict[x] += 1 def __le__(self, other): return all(self.dict[x] <= other.dict[x] for x in self.dict.keys()) And the solution becomes: [w for w in words if bag(w) <= bag(puzzle) and puzzle[4] in w]