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| References | (1 earlier) <7839376e-fc27-4299-ae63-4ddf17ef9a8a@googlegroups.com> <mailman.15068.1413977455.18130.python-list@python.org> <5447db41$0$13000$c3e8da3$5496439d@news.astraweb.com> <CAPTjJmpVk34kpL1kY=7rPiD5OpctdLsttBb5=1VyeMCQyhJ2CQ@mail.gmail.com> <5447F6F4.7080607@case.edu> |
|---|---|
| Date | 2014-10-23 05:30 +1100 |
| Subject | Re: (test) ? a:b |
| From | Chris Angelico <rosuav@gmail.com> |
| Newsgroups | comp.lang.python |
| Message-ID | <mailman.15089.1414002611.18130.python-list@python.org> (permalink) |
On Thu, Oct 23, 2014 at 5:27 AM, Matthew Ruffalo <mmr15@case.edu> wrote: > On 10/22/2014 12:40 PM, Chris Angelico wrote: >> That's true when it's fundamentally arithmetic. But part of that >> readability difference is the redundancy in the second one. What if it >> weren't so redundant? >> >> 'Negative' if x < 0 else 'Low' if x < 10 else 'Mid' if x < 20 else 'High' >> >> You can't easily turn that into a dict lookup, nor indexing. It's >> either a chained if/elif tree or nested if/else expressions, which >> come to the same thing. > No, you can't turn that into a dict lookup, but this is one of the > canonical use cases for the bisect module: > >>>> from bisect import bisect >>>> breakpoints = [0, 10, 20] >>>> labels = ['Negative', 'Low', 'Mid', 'High'] >>>> values = [-5, 5, 15, 25] >>>> [labels[bisect(breakpoints, value)] for value in values] > ['Negative', 'Low', 'Mid', 'High'] > > It's also worth noting that using bisect is O(log(n)) instead of O(n), > but if you're going to hit a point where the asymptotic behavior matters > I'm sure you will have long since abandoned a manually-written if/elif > chain. Indeed. If the performance is making any difference, something's gone wrong. I'm seeing that as not significantly clearer than the chained if/else statement or expression: you need a list of breakpoints and a list of results, which need to be kept in sync. But there's probably no ideal solution to this. ChrisA
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(test) ? a:b "ast" <nomail@invalid.com> - 2014-10-22 10:29 +0200
Re: (test) ? a:b buscacio@gmail.com - 2014-10-22 02:05 -0700
Re: (test) ? a:b "ast" <nomail@invalid.com> - 2014-10-22 11:14 +0200
Re: (test) ? a:b Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-10-22 12:45 +0100
Re: (test) ? a:b "ast" <nomail@invalid.com> - 2014-10-27 09:01 +0100
Re: (test) ? a:b Michael Torrie <torriem@gmail.com> - 2014-10-22 11:16 -0600
Re: (test) ? a:b Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-10-23 11:44 +1100
Re: (test) ? a:b Chris Angelico <rosuav@gmail.com> - 2014-10-22 20:15 +1100
Re: (test) ? a:b Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-10-22 10:16 +0100
Re: (test) ? a:b Chris Angelico <rosuav@gmail.com> - 2014-10-22 20:27 +1100
Re: (test) ? a:b Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-10-23 16:46 +1300
Re: (test) ? a:b MRAB <python@mrabarnett.plus.com> - 2014-10-23 11:12 +0100
Re: (test) ? a:b "ast" <nomail@invalid.com> - 2014-10-24 08:38 +0200
Re: (test) ? a:b Michael Torrie <torriem@gmail.com> - 2014-10-25 19:04 -0600
Re: (test) ? a:b Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-10-27 22:04 +1300
Re: (test) ? a:b Chris Angelico <rosuav@gmail.com> - 2014-10-26 12:20 +1100
Re: (test) ? a:b Michael Torrie <torriem@gmail.com> - 2014-10-25 21:05 -0600
Re: (test) ? a:b Ned Batchelder <ned@nedbatchelder.com> - 2014-10-22 07:30 -0400
Re: (test) ? a:b Marko Rauhamaa <marko@pacujo.net> - 2014-10-22 14:41 +0300
Re: (test) ? a:b Rustom Mody <rustompmody@gmail.com> - 2014-10-22 06:16 -0700
Re: (test) ? a:b "BartC" <bc@freeuk.com> - 2014-10-22 19:08 +0100
Re: (test) ? a:b Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-10-22 19:55 -0400
Re: (test) ? a:b "BartC" <bc@freeuk.com> - 2014-10-23 11:50 +0100
Re: (test) ? a:b Marko Rauhamaa <marko@pacujo.net> - 2014-10-23 16:44 +0300
Re: (test) ? a:b Ian Kelly <ian.g.kelly@gmail.com> - 2014-10-23 08:24 -0600
Re: (test) ? a:b Alain Ketterlin <alain@dpt-info.u-strasbg.fr> - 2014-10-23 16:41 +0200
Re: (test) ? a:b Marko Rauhamaa <marko@pacujo.net> - 2014-10-23 19:20 +0300
Re: (test) ? a:b Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-10-24 19:38 +1100
Re: (test) ? a:b Chris Angelico <rosuav@gmail.com> - 2014-10-24 19:45 +1100
Re: (test) ? a:b Marko Rauhamaa <marko@pacujo.net> - 2014-10-24 12:37 +0300
Re: (test) ? a:b Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-10-25 00:07 +1100
Re: (test) ? a:b Ian Kelly <ian.g.kelly@gmail.com> - 2014-10-24 12:22 -0600
Re: (test) ? a:b Marko Rauhamaa <marko@pacujo.net> - 2014-10-24 21:46 +0300
Re: (test) ? a:b Dan Stromberg <drsalists@gmail.com> - 2014-10-24 10:20 -0700
Re: (test) ? a:b alister <alister.nospam.ware@ntlworld.com> - 2014-10-24 20:58 +0000
Re: (test) ? a:b Marko Rauhamaa <marko@pacujo.net> - 2014-10-25 00:02 +0300
Re: (test) ? a:b Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-10-25 16:03 +1100
Re: (test) ? a:b Chris Angelico <rosuav@gmail.com> - 2014-10-25 16:25 +1100
Re: (test) ? a:b Ned Batchelder <ned@nedbatchelder.com> - 2014-10-25 07:58 -0400
Re: (test) ? a:b Ian Kelly <ian.g.kelly@gmail.com> - 2014-10-25 07:53 -0600
Re: (test) ? a:b Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-10-25 14:11 -0400
Re: (test) ? a:b alister <alister.nospam.ware@ntlworld.com> - 2014-10-25 19:49 +0000
Re: (test) ? a:b Ben Finney <ben+python@benfinney.id.au> - 2014-10-26 07:45 +1100
Re: (test) ? a:b Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-10-26 11:10 +1100
Re: (test) ? a:b Ben Finney <ben+python@benfinney.id.au> - 2014-10-26 12:03 +1100
Re: (test) ? a:b Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-10-26 15:15 +1100
Re: (test) ? a:b Chris Angelico <rosuav@gmail.com> - 2014-10-26 15:34 +1100
Re: (test) ? a:b Terry Reedy <tjreedy@udel.edu> - 2014-10-26 17:12 -0400
Re: (test) ? a:b Ben Finney <ben+python@benfinney.id.au> - 2014-10-27 11:38 +1100
Re: (test) ? a:b MRAB <python@mrabarnett.plus.com> - 2014-10-27 01:40 +0000
Re: (test) ? a:b Rustom Mody <rustompmody@gmail.com> - 2014-10-26 19:19 -0700
Re: (test) ? a:b Ben Finney <ben+python@benfinney.id.au> - 2014-10-26 12:10 +1100
Re: (test) ? a:b Joshua Landau <joshua@landau.ws> - 2014-10-27 01:55 +0000
Re: (test) ? a:b Ben Finney <ben+python@benfinney.id.au> - 2014-10-27 13:28 +1100
Re: (test) ? a:b Rustom Mody <rustompmody@gmail.com> - 2014-10-26 19:38 -0700
Re: (test) ? a:b Joshua Landau <joshua@landau.ws> - 2014-10-27 02:43 +0000
Re: (test) ? a:b Ben Finney <ben+python@benfinney.id.au> - 2014-10-27 13:56 +1100
Re: (test) ? a:b Dan Stromberg <drsalists@gmail.com> - 2014-10-25 15:34 -0700
Re: (test) ? a:b Ben Finney <ben+python@benfinney.id.au> - 2014-10-26 10:53 +1100
Re: (test) ? a:b Chris Angelico <rosuav@gmail.com> - 2014-10-26 11:01 +1100
Re: (test) ? a:b Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-10-26 01:09 +0100
Re: (test) ? a:b Chris Angelico <rosuav@gmail.com> - 2014-10-26 11:13 +1100
Re: (test) ? a:b Vito De Tullio <vito.detullio@gmail.com> - 2014-10-23 06:55 +0200
Re: (test) ? a:b Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-10-23 03:28 +1100
Re: (test) ? a:b Chris Angelico <rosuav@gmail.com> - 2014-10-23 03:40 +1100
Re: (test) ? a:b alister <alister.nospam.ware@ntlworld.com> - 2014-10-22 18:03 +0000
Re: (test) ? a:b Matthew Ruffalo <mmr15@case.edu> - 2014-10-22 14:27 -0400
Re: (test) ? a:b Chris Angelico <rosuav@gmail.com> - 2014-10-23 05:30 +1100
Re: (test) ? a:b Ned Batchelder <ned@nedbatchelder.com> - 2014-10-22 16:11 -0400
Re: (test) ? a:b Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-10-22 12:41 +0100
Re: (test) ? a:b alister <alister.nospam.ware@ntlworld.com> - 2014-10-22 15:12 +0000
Re: (test) ? a:b Chris Angelico <rosuav@gmail.com> - 2014-10-23 02:18 +1100
Re: (test) ? a:b alister <alister.nospam.ware@ntlworld.com> - 2014-10-22 15:24 +0000
Re: (test) ? a:b Dan Stromberg <drsalists@gmail.com> - 2014-10-22 09:09 -0700
Re: (test) ? a:b Tobiah <toby@tobiah.org> - 2014-10-24 10:23 -0700
Re: (test) ? a:b Chris Angelico <rosuav@gmail.com> - 2014-10-25 04:27 +1100
Re: (test) ? a:b Tobiah <toby@tobiah.org> - 2014-10-24 11:31 -0700
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