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| Date | Mon, 20 Jun 2011 20:29:02 -0700 |
| From | Ethan Furman <ethan@stoneleaf.us> |
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| Subject | Re: Is there any advantage or disadvantage to using sets over list comps to ensure a list of unique entries? |
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Steven D'Aprano wrote: > On Mon, 20 Jun 2011 12:43:52 -0700, deathweaselx86 wrote: >> I've been converting lists to sets, then back to lists again to get >> unique lists. >> >> I used to use list comps to do this instead. >>>>> foo = ['1','2','3'] >>>>> bar = ['2','5'] >>>>> foo.extend([a for a in bar if a not in foo]) foo >> ['1', '2', '3', '5'] >> >> Is there any performance hit to using one of these methods over the >> other for rather large lists? > > Absolutely! > > For small lists, it really doesn't matter what you do. This probably only > matters beyond a few tens of thousands of items. Depends on the complexity of the object. It only took a couple thousand dbf records to notice a *huge* slowdown using 'in' tests on regular lists. ~Ethan~
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Is there any advantage or disadvantage to using sets over list comps to ensure a list of unique entries? deathweaselx86 <deathweasel@gmail.com> - 2011-06-20 12:43 -0700
Re: Is there any advantage or disadvantage to using sets over list comps to ensure a list of unique entries? Ian Kelly <ian.g.kelly@gmail.com> - 2011-06-20 13:59 -0600
Re: Is there any advantage or disadvantage to using sets over list comps to ensure a list of unique entries? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-06-21 01:10 +0000
Re: Is there any advantage or disadvantage to using sets over list comps to ensure a list of unique entries? Ethan Furman <ethan@stoneleaf.us> - 2011-06-20 20:29 -0700
Re: Is there any advantage or disadvantage to using sets over list comps to ensure a list of unique entries? rusi <rustompmody@gmail.com> - 2011-06-20 20:59 -0700
Re: Is there any advantage or disadvantage to using sets over list comps to ensure a list of unique entries? Raymond Hettinger <python@rcn.com> - 2011-06-25 01:05 -0700
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