Python - Speed up generation of permutations of a list (and process of checking if permuations in Dict) -

i need faster way generate permutations of list, check if each 1 in dictionary.

        x in range (max_combo_len, 0, -1):             possible_combos = []             permutations = list(itertools.permutations(bag,x))             item in permutations:                 possible_combos.append(" ".join(item))             #then check see if each possible combo in specific dict 

if helps, lists going lists of strings. ['such as', 'this', 'one']

my solution works, it's slow. need stop using python, thought i'd run experts first!

best, gary

i can't test without better input cases, here few improvements:

for x in xrange(max_combo_len, 0, -1):     possible_combos = (" ".join(item) item in itertools.permutations(bag,x))     #then check see if each possible combo in specific dict     combos =  (c c in possible_combos if c in specific_dict) 

first, assuming you're using python 2.x, xrange not constructing explicit list, rather yielding each x need it.

more importantly, can throw main effort generator expressions , have yield values on demand.