3 ms·

It's not

andybak 12y ago
Are we sure?: http://stackoverflow.com/questions/3055477/how-slow-is-pythons-string-concatenation-vs-str-join http://stackoverflow.com/questions/3055477/how-slow-is-pytho...
- Luyt 12y ago
  Some of the examples in that SO post are outdated. However, list joining is faster that string concatenation, but not by much. Assembling a 110 MB string: from timeit import Timer try: from StringIO import StringIO except ImportError: from io import StringIO nr = 1200000 data = "The Quick Brown Fox Jumps Over The Lazy Dog: Woven silk pyjamas exchanged for blue quartz.\n" # contruct a list first, then join def dolist(): s = [] a = s.append i = 0 while i < nr: a(data) i += 1 s = "".join(s) print("%s chars (joined list)" % len(s)) # string concatenation fest def dostr(): s = "" i = 0 while i < nr: s += data i += 1 print("%s chars (string concatenation)" % len(s)) # use a string as a file def dostringio(): buf = StringIO() w = buf.write i = 0 while i < nr: w(data) i += 1 s = buf.getvalue() print("%s chars (cStringIO)" % len(s)) if 1: tlist = Timer("dolist()", "from __main__ import dolist") print("the joined list took %.2f seconds" % tlist.timeit(2)) tstr = Timer("dostr()", "from __main__ import dostr") print("the concatenation fest took %.2f seconds" % tstr.timeit(2)) tlist = Timer("dostringio()", "from __main__ import dostringio") print("the cStringIO approach took %.2f seconds" % tlist.timeit(2)) else: @profile def callall(): # For use with a profiler (eg, kernprof.py/lineprof) for i in xrange(2): dolist() dostr() dostringio() callall() Result: (user@air) /Users/user/Prj/python $ python3 stringplakbenchmark.py 109200000 chars (joined list) 109200000 chars (joined list) the joined list took 1.12 seconds 109200000 chars (string concatenation) 109200000 chars (string concatenation) the concatenation fest took 1.76 seconds 109200000 chars (cStringIO) 109200000 chars (cStringIO) the cStringIO approach took 1.45 seconds (user@air) /Users/user/Prj/python $ python2.7 stringplakbenchmark.py 109200000 chars (joined list) 109200000 chars (joined list) the joined list took 0.99 seconds 109200000 chars (string concatenation) 109200000 chars (string concatenation) the concatenation fest took 1.33 seconds 109200000 chars (cStringIO) 109200000 chars (cStringIO) the cStringIO approach took 5.21 seconds (user@air) /Users/user/Prj/python $ python2.6 stringplakbenchmark.py 109200000 chars (joined list) 109200000 chars (joined list) the joined list took 0.95 seconds 109200000 chars (string concatenation) 109200000 chars (string concatenation) the concatenation fest took 1.39 seconds 109200000 chars (cStringIO) 109200000 chars (cStringIO) the cStringIO approach took 5.54 seconds

It's not

Are we sure?: http://stackoverflow.com/questions/3055477/how-slow-is-pythons-string-concatenation-vs-str-join http://stackoverflow.com/questions/3055477/how-slow-is-pytho...

Luyt 12y ago
Some of the examples in that SO post are outdated. However, list joining is faster that string concatenation, but not by much. Assembling a 110 MB string: from timeit import Timer try: from StringIO import StringIO except ImportError: from io import StringIO nr = 1200000 data = "The Quick Brown Fox Jumps Over The Lazy Dog: Woven silk pyjamas exchanged for blue quartz.\n" # contruct a list first, then join def dolist(): s = [] a = s.append i = 0 while i < nr: a(data) i += 1 s = "".join(s) print("%s chars (joined list)" % len(s)) # string concatenation fest def dostr(): s = "" i = 0 while i < nr: s += data i += 1 print("%s chars (string concatenation)" % len(s)) # use a string as a file def dostringio(): buf = StringIO() w = buf.write i = 0 while i < nr: w(data) i += 1 s = buf.getvalue() print("%s chars (cStringIO)" % len(s)) if 1: tlist = Timer("dolist()", "from __main__ import dolist") print("the joined list took %.2f seconds" % tlist.timeit(2)) tstr = Timer("dostr()", "from __main__ import dostr") print("the concatenation fest took %.2f seconds" % tstr.timeit(2)) tlist = Timer("dostringio()", "from __main__ import dostringio") print("the cStringIO approach took %.2f seconds" % tlist.timeit(2)) else: @profile def callall(): # For use with a profiler (eg, kernprof.py/lineprof) for i in xrange(2): dolist() dostr() dostringio() callall() Result: (user@air) /Users/user/Prj/python $ python3 stringplakbenchmark.py 109200000 chars (joined list) 109200000 chars (joined list) the joined list took 1.12 seconds 109200000 chars (string concatenation) 109200000 chars (string concatenation) the concatenation fest took 1.76 seconds 109200000 chars (cStringIO) 109200000 chars (cStringIO) the cStringIO approach took 1.45 seconds (user@air) /Users/user/Prj/python $ python2.7 stringplakbenchmark.py 109200000 chars (joined list) 109200000 chars (joined list) the joined list took 0.99 seconds 109200000 chars (string concatenation) 109200000 chars (string concatenation) the concatenation fest took 1.33 seconds 109200000 chars (cStringIO) 109200000 chars (cStringIO) the cStringIO approach took 5.21 seconds (user@air) /Users/user/Prj/python $ python2.6 stringplakbenchmark.py 109200000 chars (joined list) 109200000 chars (joined list) the joined list took 0.95 seconds 109200000 chars (string concatenation) 109200000 chars (string concatenation) the concatenation fest took 1.39 seconds 109200000 chars (cStringIO) 109200000 chars (cStringIO) the cStringIO approach took 5.54 seconds