Sometimes, it looks like list comprehension is not the best thing to use !
I made a little test based on the answer people gave to this topic, tested on a random generated list. Here is the generation of the list (there's probably a better way to do, but it's not the point) :
good_list = ('.jpg','.jpeg','.gif','.bmp','.png')import randomimport stringmy_origin_list = []for i in xrange(10000): fname = ''.join(random.choice(string.lowercase) for i in range(random.randrange(10))) if random.getrandbits(1): fext = random.choice(good_list) else: fext = "."+''.join(random.choice(string.lowercase) for i in range(3)) my_origin_list.append((fname + fext, random.randrange(1000), fext))And here we go
# Paranddef f1(): return [e for e in my_origin_list if e[2] in good_list], [e for e in my_origin_list if not e[2] in good_list]# dbrdef f2(): a, b = list(), list() for e in my_origin_list: if e[2] in good_list: a.append(e) else: b.append(e) return a, b# John La Rooydef f3(): a, b = list(), list() for e in my_origin_list: (b, a)[e[2] in good_list].append(e) return a, b# Ants Aasmadef f4(): l1, l2 = tee((e[2] in good_list, e) for e in my_origin_list) return [i for p, i in l1 if p], [i for p, i in l2 if not p]# My personal way to dodef f5(): a, b = zip(*[(e, None) if e[2] in good_list else (None, e) for e in my_origin_list]) return list(filter(None, a)), list(filter(None, b))# BJ Homerdef f6(): return filter(lambda e: e[2] in good_list, my_origin_list), filter(lambda e: not e[2] in good_list, my_origin_list)Using the cmpthese function, the best result is the dbr answer :
f1 204/s -- -5% -14% -15% -20% -26%f6 215/s 6% -- -9% -11% -16% -22%f3 237/s 16% 10% -- -2% -7% -14%f4 240/s 18% 12% 2% -- -6% -13%f5 255/s 25% 18% 8% 6% -- -8%f2 277/s 36% 29% 17% 15% 9% --