python - Split a list into nested lists on a value -
say have list so:
[1, 4, none, 6, 9, none, 3, 9, 4 ] i decide split nested lists on none, this:
[ [ 1, 4 ], [ 6, 9 ], [ 3, 9, 4 ] ] of course, have wanted on (9, none) in case, have got:
[ [ 1, 4 ], [ 6 ], [ 3 ], [ 4 ] ] this trivial using list append through iteration ( in loop )
i interested know whether can done in faster - list comprehension?
if not, why not ( example, list comprehension cannot return more 1 list element per iteration? )
>>> def isplit(iterable,splitters): return [list(g) k,g in itertools.groupby(iterable,lambda x:x in splitters) if not k] >>> isplit(l,(none,)) [[1, 4], [6, 9], [3, 9, 4]] >>> isplit(l,(none,9)) [[1, 4], [6], [3], [4]] benchmark code:
import timeit kabie=("isplit_kabie", """ import itertools def isplit_kabie(iterable,splitters): return [list(g) k,g in itertools.groupby(iterable,lambda x:x in splitters) if not k] """ ) ssplit=("ssplit", """ def ssplit(seq,splitters): seq=list(seq) if splitters , seq: result=[] begin=0 end in range(len(seq)): if seq[end] in splitters: if end > begin: result.append(seq[begin:end]) begin=end+1 if begin<len(seq): result.append(seq[begin:]) return result return [seq] """ ) ssplit2=("ssplit2", """ def ssplit2(seq,splitters): seq=list(seq) if splitters , seq: splitters=set(splitters).intersection(seq) if splitters: result=[] begin=0 end in range(len(seq)): if seq[end] in splitters: if end > begin: result.append(seq[begin:end]) begin=end+1 if begin<len(seq): result.append(seq[begin:]) return result return [seq] """ ) emile=("magicsplit", """ def _itersplit(l, *splitters): current = [] item in l: if item in splitters: yield current current = [] else: current.append(item) yield current def magicsplit(l, splitters): return [subl subl in _itersplit(l, *splitters) if subl] """ ) emile_improved=("magicsplit2", """ def _itersplit(l, *splitters): current = [] item in l: if item in splitters: if current: yield current current = [] else: current.append(item) if current: yield current def magicsplit2(l, splitters): if splitters , l: return [i in _itersplit(l, *splitters)] return [list(l)] """ ) karl=("ssplit_karl", """ def ssplit_karl(original,splitters): indices = [i (i, x) in enumerate(original) if x in splitters] ends = indices + [len(original)] begins = [0] + [x + 1 x in indices] return [original[begin:end] (begin, end) in zip(begins, ends)] """ ) ryan=("split_on", """ functools import reduce def split_on (seq, delims, remove_empty=true): '''split seq lists using delims delimiting elements. example, split_on(delims=2, list=xrange(0,5)) yields [ [0,1], [3,4] ]. delims can either single delimiting element or list or tuple of multiple delimiting elements. if wish use list or tuple delimiter, must enclose in list or tuple. if remove_empty false, consecutive delimiter elements or delimiter elements @ beginning or end of longlist''' delims=set(delims) def reduce_fun(lists, elem): if elem in delims: if remove_empty , lists[-1] == []: # avoid adding multiple empty lists pass else: lists.append([]) else: lists[-1].append(elem) return lists result_list = reduce(reduce_fun, seq, [ [], ]) # maybe remove trailing empty list if remove_empty , result_list[-1] == []: result_list.pop() return result_list """ ) cases=(kabie, emile, emile_improved, ssplit ,ssplit2 ,ryan) data=( ([1, 4, none, 6, 9, none, 3, 9, 4 ],(none,)), ([1, 4, none, 6, 9, none, 3, 9, 4 ]*5,{none,9,7}), ((),()), (range(1000),()), ("split me",('','')), ("split me "*100,' '), ("split me,"*100,' ,'*20), ("split me, please!"*100,' ,!'), (range(100),range(100)), (range(100),range(101,1000)), (range(100),range(50,150)), (list(range(100))*30,(99,)), ) params="seq,splitters" def benchmark(func,code,data,params='',times=10000,rounds=3,debug=''): assert(func.isidentifier()) tester = timeit.timer(stmt='{func}({params})'.format( func=func,params=params), setup="{code}\n".format(code=code)+ (params , "{params}={data}\n".format(params=params,data=data)) + (debug , """ret=repr({func}({params})) print({func}.__name__.rjust(16),":",ret[:30]+"..."+ret[-15:] if len(ret)>50 else ret) """.format(func=func,params=params))) results = [tester.timeit(times) in range(rounds)] if not debug: print("{:>16s} takes:{:6.4f},avg:{:.2e},best:{:.4f},worst:{:.4f}".format( func,sum(results),sum(results)/times/rounds,min(results),max(results))) def testall(cases,data,params='',times=10000,rounds=3,debug=''): if debug: times,rounds = 1,1 dat in data: sdat = tuple(map(repr,dat)) print("{}x{} times:".format(times,rounds), ','.join("{}".format(d[:8]+"..."+d[-5:] if len(d)>16 else d)for d in map(repr,dat))) func,code in cases: benchmark(func,code,dat,params,times,rounds,debug) if __name__=='__main__': testall(cases,data,params,500,10)#,debug=true) output on i3-530, windows7, python 3.1.2:
500x10 times: [1, 4, n...9, 4],(none,) isplit_kabie takes:0.0605,avg:1.21e-05,best:0.0032,worst:0.0074 magicsplit takes:0.0287,avg:5.74e-06,best:0.0016,worst:0.0036 magicsplit2 takes:0.0174,avg:3.49e-06,best:0.0017,worst:0.0018 ssplit takes:0.0149,avg:2.99e-06,best:0.0015,worst:0.0016 ssplit2 takes:0.0198,avg:3.96e-06,best:0.0019,worst:0.0021 split_on takes:0.0229,avg:4.59e-06,best:0.0023,worst:0.0024 500x10 times: [1, 4, n...9, 4],{9, none, 7} isplit_kabie takes:0.1448,avg:2.90e-05,best:0.0144,worst:0.0146 magicsplit takes:0.0636,avg:1.27e-05,best:0.0063,worst:0.0065 magicsplit2 takes:0.0891,avg:1.78e-05,best:0.0064,worst:0.0162 ssplit takes:0.0593,avg:1.19e-05,best:0.0058,worst:0.0061 ssplit2 takes:0.1004,avg:2.01e-05,best:0.0069,worst:0.0142 split_on takes:0.0929,avg:1.86e-05,best:0.0090,worst:0.0096 500x10 times: (),() isplit_kabie takes:0.0041,avg:8.14e-07,best:0.0004,worst:0.0004 magicsplit takes:0.0040,avg:8.04e-07,best:0.0004,worst:0.0004 magicsplit2 takes:0.0022,avg:4.35e-07,best:0.0002,worst:0.0002 ssplit takes:0.0023,avg:4.59e-07,best:0.0002,worst:0.0003 ssplit2 takes:0.0023,avg:4.53e-07,best:0.0002,worst:0.0002 split_on takes:0.0072,avg:1.45e-06,best:0.0007,worst:0.0009 500x10 times: range(0, 1000),() isplit_kabie takes:0.8892,avg:1.78e-04,best:0.0881,worst:0.0895 magicsplit takes:0.6614,avg:1.32e-04,best:0.0654,worst:0.0673 magicsplit2 takes:0.0958,avg:1.92e-05,best:0.0094,worst:0.0099 ssplit takes:0.0943,avg:1.89e-05,best:0.0093,worst:0.0095 ssplit2 takes:0.0943,avg:1.89e-05,best:0.0093,worst:0.0096 split_on takes:1.3348,avg:2.67e-04,best:0.1328,worst:0.1340 500x10 times: 'split me',('', '') isplit_kabie takes:0.0234,avg:4.68e-06,best:0.0023,worst:0.0024 magicsplit takes:0.0126,avg:2.52e-06,best:0.0012,worst:0.0013 magicsplit2 takes:0.0138,avg:2.76e-06,best:0.0013,worst:0.0015 ssplit takes:0.0119,avg:2.39e-06,best:0.0012,worst:0.0012 ssplit2 takes:0.0075,avg:1.50e-06,best:0.0007,worst:0.0008 split_on takes:0.0191,avg:3.83e-06,best:0.0018,worst:0.0023 500x10 times: 'split m... me ',' ' isplit_kabie takes:2.0803,avg:4.16e-04,best:0.2060,worst:0.2098 magicsplit takes:0.9219,avg:1.84e-04,best:0.0920,worst:0.0925 magicsplit2 takes:1.0221,avg:2.04e-04,best:0.1018,worst:0.1034 ssplit takes:0.8294,avg:1.66e-04,best:0.0818,worst:0.0834 ssplit2 takes:0.9911,avg:1.98e-04,best:0.0983,worst:0.1014 split_on takes:1.5672,avg:3.13e-04,best:0.1543,worst:0.1694 500x10 times: 'split m... me,',' , , , ... , ,' isplit_kabie takes:2.1847,avg:4.37e-04,best:0.2164,worst:0.2275 magicsplit takes:3.7135,avg:7.43e-04,best:0.3693,worst:0.3783 magicsplit2 takes:3.8104,avg:7.62e-04,best:0.3795,worst:0.3884 ssplit takes:0.9522,avg:1.90e-04,best:0.0939,worst:0.0956 ssplit2 takes:1.0140,avg:2.03e-04,best:0.1009,worst:0.1023 split_on takes:1.5747,avg:3.15e-04,best:0.1563,worst:0.1615 500x10 times: 'split m...ase!',' ,!' isplit_kabie takes:3.3443,avg:6.69e-04,best:0.3324,worst:0.3380 magicsplit takes:2.0594,avg:4.12e-04,best:0.2054,worst:0.2076 magicsplit2 takes:2.1850,avg:4.37e-04,best:0.2180,worst:0.2191 ssplit takes:1.4881,avg:2.98e-04,best:0.1484,worst:0.1493 ssplit2 takes:1.8779,avg:3.76e-04,best:0.1868,worst:0.1920 split_on takes:2.9596,avg:5.92e-04,best:0.2946,worst:0.2980 500x10 times: range(0, 100),range(0, 100) isplit_kabie takes:0.9445,avg:1.89e-04,best:0.0933,worst:0.1023 magicsplit takes:0.5878,avg:1.18e-04,best:0.0583,worst:0.0593 magicsplit2 takes:0.5597,avg:1.12e-04,best:0.0554,worst:0.0588 ssplit takes:0.8568,avg:1.71e-04,best:0.0852,worst:0.0874 ssplit2 takes:0.1399,avg:2.80e-05,best:0.0121,worst:0.0242 split_on takes:0.1462,avg:2.92e-05,best:0.0145,worst:0.0148 500x10 times: range(0, 100),range(101, 1000) isplit_kabie takes:19.9749,avg:3.99e-03,best:1.9789,worst:2.0330 magicsplit takes:9.4997,avg:1.90e-03,best:0.9369,worst:0.9640 magicsplit2 takes:9.4394,avg:1.89e-03,best:0.9267,worst:0.9665 ssplit takes:19.2363,avg:3.85e-03,best:1.8936,worst:1.9516 ssplit2 takes:0.2032,avg:4.06e-05,best:0.0201,worst:0.0205 split_on takes:0.3329,avg:6.66e-05,best:0.0323,worst:0.0344 500x10 times: range(0, 100),range(50, 150) isplit_kabie takes:1.1394,avg:2.28e-04,best:0.1130,worst:0.1153 magicsplit takes:0.7288,avg:1.46e-04,best:0.0721,worst:0.0760 magicsplit2 takes:0.7220,avg:1.44e-04,best:0.0705,worst:0.0774 ssplit takes:1.0835,avg:2.17e-04,best:0.1059,worst:0.1116 ssplit2 takes:0.1092,avg:2.18e-05,best:0.0105,worst:0.0116 split_on takes:0.1639,avg:3.28e-05,best:0.0162,worst:0.0168 500x10 times: [0, 1, 2..., 99],(99,) isplit_kabie takes:3.2579,avg:6.52e-04,best:0.3225,worst:0.3360 magicsplit takes:2.2937,avg:4.59e-04,best:0.2274,worst:0.2344 magicsplit2 takes:2.6054,avg:5.21e-04,best:0.2587,worst:0.2642 ssplit takes:1.5251,avg:3.05e-04,best:0.1495,worst:0.1729 ssplit2 takes:1.7298,avg:3.46e-04,best:0.1696,worst:0.1858 split_on takes:4.1041,avg:8.21e-04,best:0.4033,worst:0.4291 slightly modified ryan's code, hope don't mind. ssplit based on idea of karl. added statements handling special cases became ssplit2 best solution may provide.
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