Re: a better way to invert a list?

From	Paul Rubin <no.email@nospam.invalid>
Newsgroups	comp.lang.python
Subject	Re: a better way to invert a list?
References	<2215eefd-3677-4459-8656-aa04978f6f3f@g7g2000pro.googlegroups.com>
Date	2011-04-06 12:51 -0700
Message-ID	<7xwrj7kvjv.fsf@ruckus.brouhaha.com> (permalink)
Organization	Nightsong/Fort GNOX

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scattered <tooscattered@gmail.com> writes:
> def invert(p):
> 	return [ j for (i,j) in sorted(zip(p,range(len(p))))]


   return [j for i,j in sorted(enumerate(p), key=itemgetter(1))]

looks a little cleaner to me.

    In Haskell or ML, you can use patterns that contain wild
    cards that play a role in the pattern-matching but don't establish any
    binding. Can that be done in Python?

Not as much.  You could say something like

         sorted(enumerate(p), key=lambda(_,j): j)

which gets the meaning across (it binds the symbol "_" though this
doesn't escape the lambda).

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a better way to invert a list? scattered <tooscattered@gmail.com> - 2011-04-05 14:17 -0700
  Re: a better way to invert a list? Ian Kelly <ian.g.kelly@gmail.com> - 2011-04-05 15:46 -0600
    Re: a better way to invert a list? scattered <tooscattered@gmail.com> - 2011-04-05 16:24 -0700
      Re: a better way to invert a list? Glazner <yoavglazner@gmail.com> - 2011-04-06 01:48 -0700
        Re: a better way to invert a list? scattered <tooscattered@gmail.com> - 2011-04-06 02:48 -0700
        Re: a better way to invert a list? Peter Otten <__peter__@web.de> - 2011-04-06 11:58 +0200
    Re: a better way to invert a list? Raymond Hettinger <python@rcn.com> - 2011-04-05 17:07 -0700
  Re: a better way to invert a list? Paul Rubin <no.email@nospam.invalid> - 2011-04-06 12:51 -0700
    Re: a better way to invert a list? Ian Kelly <ian.g.kelly@gmail.com> - 2011-04-06 14:08 -0600

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