todddeluca

15년 전discuss

Here are performance numbers for a variety of approaches using a list of length 256. You can see that having a local reference to the global chr function (as discussed in the article) can give a slight speed boost. Using join() in conjunction with map() performs fairly well.

  python -m timeit -s 'l = range(256);' '"".join([chr(i) for i in l])'
  # 10000 loops, best of 3: 80.5 usec per loop
  python -m timeit -s 'l = range(256); lchr = chr' '"".join([lchr(i) for i in l])'
  # 10000 loops, best of 3: 75 usec per loop
  python -m timeit -s 'import itertools; l = range(256); lchr = chr' '"".join(itertools.imap(chr, l))'
  # 10000 loops, best of 3: 52.8 usec per loop
  python -m timeit -s 'l = range(256); lchr = chr' '"".join(map(chr, l))'
  # 10000 loops, best of 3: 48.9 usec per loop
  python -m timeit -s 'l = range(256); lchr = chr' '"".join(lchr(i) for i in l)'
  # 10000 loops, best of 3: 87.2 usec per loop
  python -m timeit -s 'l = range(256); lchr = chr' '
  s = ""
  for i in l:
    s += lchr(i)
  '
  # 10000 loops, best of 3: 64.2 usec per loop

todddeluca

15년 전discuss

To avoid confusing newbies, str() does not concatenate a list (or generator, etc.) of strings into a single string. You probably meant to call ''.join() instead.

  >>> import itertools
  >>> def f2_1(list):
  ...         return str(itertools.imap(chr, list))
  ... 
  >>> f2_1(range(10))
  '<itertools.imap object at 0x10048e850>'
  >>> def f2_2(list):
  ...         return str(chr(c) for c in list)
  ... 
  >>> f2_2(range(10))
  '<generator object <genexpr> at 0x10046b780>'

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