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Groups > comp.lang.python > #89607

Re: Lucky numbers in Python

From Cecil Westerhof <Cecil@decebal.nl>
Newsgroups comp.lang.python
Subject Re: Lucky numbers in Python
Organization Decebal Computing
References (1 earlier) <mailman.95.1430337506.3680.python-list@python.org> <87d22mbod7.fsf@Equus.decebal.nl> <mailman.103.1430347166.3680.python-list@python.org> <871tj2bi2p.fsf@Equus.decebal.nl> <mailman.110.1430362572.3680.python-list@python.org>
Date 2015-04-30 08:34 +0200
Message-ID <87r3r29lal.fsf@Equus.decebal.nl> (permalink)

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Op Thursday 30 Apr 2015 04:55 CEST schreef Ian Kelly:

> On Wed, Apr 29, 2015 at 6:01 PM, Cecil Westerhof <Cecil@decebal.nl> wrote:
>> Op Thursday 30 Apr 2015 00:38 CEST schreef Ian Kelly:
>>> In that case you can definitely omit the middle term of the slice,
>>> which will be both more concise and clearer in intent, though
>>> probably not significantly faster.
>>
>> It is certainly nit faster. It is even significantly slower. With
>> the middle term lucky_numbers(int(1e6)) takes 0.13 seconds. Without
>> it takes 14.3 seconds. Hundred times as long.
>
> That would be rather surprising, since it's the same operation being
> performed, so I did my own timing and came up with 0.25 seconds
> (best of 3) with the middle term and 0.22 seconds without.
>
> I suspect that you tested it as "del sieve[skip_count - 1 :
> skip_count]" (which would delete only one item) rather than "del
> sieve[skip_count - 1 :: skip_count]".

Yeah, that is how I interpreted omitting the middle term. But it
seemed to give the right results.

With your amendment it runs slightly faster. With 1E7 it is 8.0 and
7.7. So almost 4% faster.

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof

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Thread

Lucky numbers in Python Cecil Westerhof <Cecil@decebal.nl> - 2015-04-29 20:24 +0200
  Re: Lucky numbers in Python Ian Kelly <ian.g.kelly@gmail.com> - 2015-04-29 13:57 -0600
    Re: Lucky numbers in Python Cecil Westerhof <Cecil@decebal.nl> - 2015-04-29 23:45 +0200
      Re: Lucky numbers in Python Ian Kelly <ian.g.kelly@gmail.com> - 2015-04-29 16:38 -0600
        Re: Lucky numbers in Python Cecil Westerhof <Cecil@decebal.nl> - 2015-04-30 02:01 +0200
          Re: Lucky numbers in Python Ian Kelly <ian.g.kelly@gmail.com> - 2015-04-29 20:55 -0600
            Re: Lucky numbers in Python Cecil Westerhof <Cecil@decebal.nl> - 2015-04-30 08:34 +0200
      Re: Lucky numbers in Python Chris Kaynor <ckaynor@zindagigames.com> - 2015-04-29 15:56 -0700
    Re: Lucky numbers in Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-30 10:11 +1000
      Re: Lucky numbers in Python Ian Kelly <ian.g.kelly@gmail.com> - 2015-04-29 21:08 -0600
  Re: Lucky numbers in Python Cecil Westerhof <Cecil@decebal.nl> - 2015-04-30 20:55 +0200
    Re: Lucky numbers in Python Dave Angel <davea@davea.name> - 2015-04-30 15:28 -0400

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