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Re: Question about `list.insert`

References <4041bba7-91bc-4803-9150-2fcf14ecb5a9@googlegroups.com>
Date 2014-02-06 20:52 -0800
Subject Re: Question about `list.insert`
From Dan Stromberg <drsalists@gmail.com>
Newsgroups comp.lang.python
Message-ID <mailman.6480.1391748751.18130.python-list@python.org> (permalink)

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On Thu, Feb 6, 2014 at 3:59 PM, cool-RR <ram.rachum@gmail.com> wrote:
> Hi,
>
> I'm curious. If I append an item to a list from the left using `list.insert`, will Python always move the entire list one item to the right (which can be super-slow) or will it check first to see whether it can just allocate more memory to the left of the list and put the item there, saving a lot of resources?

I'm pretty sure it'll slide all the existing elements right one
position, and add at the leftmost position just opened up - assuming
you're inserting at position 0.

As was already mentioned, collections.deque is good for this sort of
thing.  It's implemented as a fancy doubly-linked list. Or rather, a
doubly-linked list of smallish arrays/lists.

For a singly-linked list:
http://stackoverflow.com/questions/280243/python-linked-list
http://stromberg.dnsalias.org/~strombrg/linked-list/

HTH

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Thread

Question about `list.insert` cool-RR <ram.rachum@gmail.com> - 2014-02-06 15:59 -0800
  Re: Question about `list.insert` Terry Reedy <tjreedy@udel.edu> - 2014-02-06 19:40 -0500
  Re: Question about `list.insert` MRAB <python@mrabarnett.plus.com> - 2014-02-07 00:42 +0000
  Re: Question about `list.insert` Terry Reedy <tjreedy@udel.edu> - 2014-02-06 21:48 -0500
  Re:Question about `list.insert` Dave Angel <davea@davea.name> - 2014-02-06 21:54 -0500
    Re: Question about `list.insert` Roy Smith <roy@panix.com> - 2014-02-06 22:00 -0500
      Re: Question about `list.insert` Rustom Mody <rustompmody@gmail.com> - 2014-02-06 19:08 -0800
      Re: Question about `list.insert` Tim Chase <python.list@tim.thechases.com> - 2014-02-06 21:11 -0600
        Re: Question about `list.insert` Roy Smith <roy@panix.com> - 2014-02-06 22:12 -0500
          Re: Question about `list.insert` Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-02-07 17:18 +1300
      Re: Question about `list.insert` Chris Angelico <rosuav@gmail.com> - 2014-02-07 14:14 +1100
      Re: Question about `list.insert` Chris Angelico <rosuav@gmail.com> - 2014-02-07 14:20 +1100
        Re: Question about `list.insert` Rustom Mody <rustompmody@gmail.com> - 2014-02-06 19:29 -0800
          Re: Question about `list.insert` Chris Angelico <rosuav@gmail.com> - 2014-02-07 14:45 +1100
      Re: Question about `list.insert` Asaf Las <roegltd@gmail.com> - 2014-02-06 19:28 -0800
  Re: Question about `list.insert` Dan Stromberg <drsalists@gmail.com> - 2014-02-06 20:52 -0800
    Re: Question about `list.insert` Asaf Las <roegltd@gmail.com> - 2014-02-06 21:18 -0800
  Re: Question about `list.insert` Peter Otten <__peter__@web.de> - 2014-02-07 09:25 +0100

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