in-place string reversal

Fredrik Lundh fredrik at pythonware.com
Tue Mar 28 19:02:01 CEST 2006


Sion Arrowsmith wrote:

> But note that a significant chunk is the join():
>
> $ python2.4 -mtimeit '"".join(reversed("foo"))'
> 100000 loops, best of 3: 2.72 usec per loop
> $ python2.4 -mtimeit 'reversed("foo")'
> 1000000 loops, best of 3: 1.69 usec per loop

your second benchmark doesn't do any reversal, though.  it only
creates a bunch of reversed() iterator objects.

it's a little like my old faster-than-the-speed-of-light XML parser
benchmark:

> dir test.xml
...
2005-05-04  20:41           12 658 399 test.xml
...
> python -m timeit -s "import cElementTree" "matches = (elem.get('value')
for event, elem in cElementTree.iterparse('test.xml') if elem.get('name')
== 'reselectApi')"
1000 loops, best of 3: 198 usec per loop
> python -c "print 12658399 / 198e-6"
63931308080.8

(64 gigabytes per second?  who said XML was a performance hog ?)

</F>






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