Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > comp.lang.python > #90810
| References | <9ceklad15llnv3npejq9iuh91soci8aeqo@4ax.com> |
|---|---|
| Date | 2015-05-18 21:42 +0200 |
| Subject | Re: Slices time complexity |
| From | Todd <toddrjen@gmail.com> |
| Newsgroups | comp.lang.python |
| Message-ID | <mailman.113.1431978594.17265.python-list@python.org> (permalink) |
[Multipart message — attachments visible in raw view] - view raw
On May 18, 2015 9:26 PM, "Mario Figueiredo" <marfig@gmail.com> wrote: > > I'd like to understand what I'm being told about slices in > https://wiki.python.org/moin/TimeComplexity > > Particularly, what's a 'del slice' and a 'set slice' and whether this > information pertains to both CPython 2.7 and 3.4. > > From the above link it seems slices work in linear time on all cases. > And this really has a big impact on certain operations. For instance, > the code below may surprise some people when they realize it doesn't > run in linear time on 3.4: > > def minimum(values): > if len(values) == 1: > return values[0] > else: > m = minimum(values[1:]) > return m if m < values[0] else values[0] > > Other languages implement slices. I'm currently being faced with a Go > snippet that mirrors the exact code above and it does run in linear > time. > > Is there any reason why Python 3.4 implementation of slices cannot be > a near constant operation? In this case you are copying the items (or rather pointers to the items) from the list to a new list. This is inherently a O(k) operation. There are other ways to implement it. I recall the was talk of a way to get views of sequences, although this would involve keeping the original list in memory and any changes to the new list would be passed to the original (this is how numpy works) . It is also possible to do copy-on-write, which avoids altering the original list but has the same memory problems while still involving a O(k) copy operation if you want to change the list, and it is more complex to implement (this is how MATLAB works) . But to have a new list that can be edited independently requires coping something, and that will be a O(k) operation, unless you use a radically different data structure with its own limitations.
Back to comp.lang.python | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
Slices time complexity Mario Figueiredo <marfig@gmail.com> - 2015-05-18 20:23 +0100
Re: Slices time complexity Chris Angelico <rosuav@gmail.com> - 2015-05-19 05:36 +1000
Re: Slices time complexity Mario Figueiredo <marfig@gmail.com> - 2015-05-18 20:49 +0100
Re: Slices time complexity Chris Angelico <rosuav@gmail.com> - 2015-05-19 06:04 +1000
Re: Slices time complexity Todd <toddrjen@gmail.com> - 2015-05-18 21:42 +0200
Re: Slices time complexity Ian Kelly <ian.g.kelly@gmail.com> - 2015-05-18 13:49 -0600
Re: Slices time complexity Fabien <fabien.maussion@gmail.com> - 2015-05-18 21:54 +0200
Re: Slices time complexity Todd <toddrjen@gmail.com> - 2015-05-18 22:23 +0200
Re: Slices time complexity Mario Figueiredo <marfig@gmail.com> - 2015-05-18 22:04 +0100
Re: Slices time complexity Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-05-18 22:38 +0100
Re: Slices time complexity Terry Reedy <tjreedy@udel.edu> - 2015-05-18 19:04 -0400
Re: Slices time complexity Rustom Mody <rustompmody@gmail.com> - 2015-05-18 19:20 -0700
Re: Slices time complexity Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-19 15:13 +1000
Re: Slices time complexity Rustom Mody <rustompmody@gmail.com> - 2015-05-18 22:33 -0700
Re: Slices time complexity Marko Rauhamaa <marko@pacujo.net> - 2015-05-19 10:12 +0300
Re: Slices time complexity Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-19 18:16 +1000
Re: Slices time complexity Marko Rauhamaa <marko@pacujo.net> - 2015-05-19 11:39 +0300
Re: Slices time complexity Chris Angelico <rosuav@gmail.com> - 2015-05-19 18:50 +1000
Re: Slices time complexity Marko Rauhamaa <marko@pacujo.net> - 2015-05-19 12:35 +0300
Re: Slices time complexity Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-19 23:44 +1000
Re: Slices time complexity Christian Gollwitzer <auriocus@gmx.de> - 2015-05-20 23:54 +0200
Re: Slices time complexity Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-05-19 23:00 +1200
Re: Slices time complexity Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-20 11:47 +1000
Re: Slices time complexity Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2015-05-20 08:07 -0400
Re: Slices time complexity Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-19 22:42 +1000
Re: Slices time complexity Chris Angelico <rosuav@gmail.com> - 2015-05-19 23:24 +1000
Re: Slices time complexity Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-05-20 12:31 +1200
Re: Slices time complexity Ben Finney <ben+python@benfinney.id.au> - 2015-05-20 10:42 +1000
Re: Slices time complexity Marko Rauhamaa <marko@pacujo.net> - 2015-05-20 07:24 +0300
Re: Slices time complexity Rustom Mody <rustompmody@gmail.com> - 2015-05-19 21:30 -0700
Re: Slices time complexity Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-05-20 06:06 +0100
Re: Slices time complexity Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-20 15:57 +1000
Re: Slices time complexity Marko Rauhamaa <marko@pacujo.net> - 2015-05-20 09:17 +0300
Re: Slices time complexity Rustom Mody <rustompmody@gmail.com> - 2015-05-19 23:23 -0700
Re: Slices time complexity Marko Rauhamaa <marko@pacujo.net> - 2015-05-20 09:46 +0300
Re: Slices time complexity Rustom Mody <rustompmody@gmail.com> - 2015-05-20 00:03 -0700
Re: Slices time complexity Marko Rauhamaa <marko@pacujo.net> - 2015-05-20 10:45 +0300
List semantics [was Re: Slices time complexity] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-20 17:23 +1000
Re: List semantics [was Re: Slices time complexity] Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-05-20 20:54 +1200
Re: List semantics [was Re: Slices time complexity] Ned Batchelder <ned@nedbatchelder.com> - 2015-05-20 04:08 -0700
Re: List semantics [was Re: Slices time complexity] Terry Reedy <tjreedy@udel.edu> - 2015-05-20 14:42 -0400
Re: List semantics [was Re: Slices time complexity] Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-05-21 11:06 +1200
Re: List semantics [was Re: Slices time complexity] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-21 12:10 +1000
Re: Slices time complexity "Bartc" <bartc@freeuk.com> - 2015-05-20 10:56 +0100
Re: Slices time complexity Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2015-05-20 10:16 +0100
Re: Slices time complexity Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-21 15:19 +1000
Re: Slices time complexity Marko Rauhamaa <marko@pacujo.net> - 2015-05-21 09:20 +0300
Re: Slices time complexity bartc <bart4858@gmail.com> - 2015-05-21 06:34 -0700
Re: Slices time complexity MRAB <python@mrabarnett.plus.com> - 2015-05-21 17:50 +0100
Re: Slices time complexity Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-22 03:16 +1000
Re: Slices time complexity bart4858@gmail.com - 2015-05-21 12:48 -0700
Re: Slices time complexity Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-20 12:26 +1000
Re: Slices time complexity Chris Angelico <rosuav@gmail.com> - 2015-05-20 12:36 +1000
Re: Slices time complexity Rustom Mody <rustompmody@gmail.com> - 2015-05-19 20:02 -0700
Re: Slices time complexity Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-19 21:43 +1000
Re: Slices time complexity Marko Rauhamaa <marko@pacujo.net> - 2015-05-19 18:59 +0300
Re: Slices time complexity Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-20 03:46 +1000
Re: Slices time complexity Chris Angelico <rosuav@gmail.com> - 2015-05-20 04:12 +1000
Re: Slices time complexity Marko Rauhamaa <marko@pacujo.net> - 2015-05-19 21:19 +0300
Re: Slices time complexity Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-20 10:43 +1000
Re: Slices time complexity Marko Rauhamaa <marko@pacujo.net> - 2015-05-20 07:30 +0300
Re: Slices time complexity Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-20 15:33 +1000
Re: Slices time complexity Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-20 15:58 +1000
Re: Slices time complexity Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2015-05-19 15:18 +0100
Re: Slices time complexity Rustom Mody <rustompmody@gmail.com> - 2015-05-19 04:46 -0700
Re: Slices time complexity Rustom Mody <rustompmody@gmail.com> - 2015-05-19 05:14 -0700
Re: Slices time complexity Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-19 18:19 +1000
Re: Slices time complexity Rustom Mody <rustompmody@gmail.com> - 2015-05-19 04:41 -0700
Re: Slices time complexity Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-19 19:45 +1000
Re: Slices time complexity Serhiy Storchaka <storchaka@gmail.com> - 2015-05-19 13:15 +0300
Re: Slices time complexity Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2015-05-19 12:09 +0100
Re: Slices time complexity "Bartc" <bartc@freeuk.com> - 2015-05-19 15:52 +0100
Re: Slices time complexity Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-20 03:07 +1000
Re: Slices time complexity Chris Angelico <rosuav@gmail.com> - 2015-05-20 03:19 +1000
Re: Slices time complexity Mario Figueiredo <marfig@gmail.com> - 2015-05-20 20:51 +0100
Re: Slices time complexity Ian Kelly <ian.g.kelly@gmail.com> - 2015-05-20 14:33 -0600
Re: Slices time complexity Chris Angelico <rosuav@gmail.com> - 2015-05-21 06:35 +1000
Re: Slices time complexity Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-05-20 21:47 +0100
Re: Slices time complexity Mario Figueiredo <marfig@gmail.com> - 2015-05-20 22:23 +0100
Re: Slices time complexity Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-21 17:35 +1000
Re: Slices time complexity Chris Angelico <rosuav@gmail.com> - 2015-05-21 18:25 +1000
Re: Slices time complexity Ian Kelly <ian.g.kelly@gmail.com> - 2015-05-19 09:15 -0600
Re: Slices time complexity Serhiy Storchaka <storchaka@gmail.com> - 2015-05-19 22:51 +0300
csiph-web