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Groups > comp.lang.python > #61392

Re: squeeze out some performance

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On 06/12/2013 22:07, Joel Goldstick wrote:
..........
>>
>
> Not that this will speed up your code but you have this:
>
>      if not clockwise:
>          s = start
>          start = end
>          end = s
>
> Python people would write:
>      end, start = start, end

this works for some small number of variables, but on my machine with python 2.7 
I start losing with 4 variables eg

> C:\code\optichrome\74663>python -mtimeit -s"a=1;b=2;c=3;d=4" "a,b,c,d=b,c,d,a"
> 1000000 loops, best of 3: 0.206 usec per loop
>
> C:\code\optichrome\74663>python -mtimeit -s"a=1;b=2;c=3;d=4" "t=a;a=b;b=c;c=d;d=t"
> 10000000 loops, best of 3: 0.118 usec per loop


It doesn't seem to make much difference that the variables are related as I see 
a similar behaviour for simple assignments

> C:\code\optichrome\74663>python -mtimeit -s"a=1;b=2;c=3;d=4;e=5;f=6;g=7;h=8" "a,b,c,d=e,f,g,h"
> 1000000 loops, best of 3: 0.204 usec per loop
>
> C:\code\optichrome\74663>python -mtimeit -s"a=1;b=2;c=3;d=4;e=5;f=6;g=7;h=8" "a=e;b=f;c=g;d=h"
> 10000000 loops, best of 3: 0.103 usec per loop

for less than 4 variables the tuple method is faster.
-- 
Robin Becker

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squeeze out some performance Robert Voigtländer <r.voigtlaender@gmail.com> - 2013-12-06 00:47 -0800
  Re: squeeze out some performance Jeremy Sanders <jeremy@jeremysanders.net> - 2013-12-06 10:46 +0100
  Re: squeeze out some performance Chris Angelico <rosuav@gmail.com> - 2013-12-06 23:13 +1100
    Re: squeeze out some performance Robert Voigtländer <r.voigtlaender@gmail.com> - 2013-12-06 08:29 -0800
      Re: squeeze out some performance Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-12-06 16:36 +0000
        Re: squeeze out some performance Robert Voigtländer <r.voigtlaender@gmail.com> - 2013-12-06 08:44 -0800
  Re: squeeze out some performance John Ladasky <john_ladasky@sbcglobal.net> - 2013-12-06 08:52 -0800
    Re: squeeze out some performance Joel Goldstick <joel.goldstick@gmail.com> - 2013-12-06 17:07 -0500
    Re: squeeze out some performance Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-12-06 22:38 +0000
    Re: squeeze out some performance Dan Stromberg <drsalists@gmail.com> - 2013-12-06 15:01 -0800
      Re: squeeze out some performance Robert Voigtländer <r.voigtlaender@gmail.com> - 2013-12-09 06:19 -0800
        Re: squeeze out some performance Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-12-09 14:52 +0000
    Re: squeeze out some performance Robin Becker <robin@reportlab.com> - 2013-12-09 15:54 +0000
    Re: squeeze out some performance Dave Angel <davea@davea.name> - 2013-12-09 15:46 -0500
    Re: squeeze out some performance Robin Becker <robin@reportlab.com> - 2013-12-10 12:54 +0000
  Re: squeeze out some performance Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-12-09 23:57 +0000
    Re: squeeze out some performance Robert Voigtländer <r.voigtlaender@gmail.com> - 2013-12-10 04:14 -0800

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