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Re: pylint woes

From MRAB <python@mrabarnett.plus.com>
Newsgroups comp.lang.python
Subject Re: pylint woes
Date 2016-05-11 02:02 +0100
Message-ID <mailman.583.1462928532.32212.python-list@python.org> (permalink)
References (6 earlier) <ngm79s$d60$1@dont-email.me> <CAPTjJmq4Uqiz-5BO=StiMfg+jjnQyG4HPQ+Sh+qb4UWWFvLReQ@mail.gmail.com> <mailman.493.1462675848.32212.python-list@python.org> <ngtnja$cni$1@dont-email.me> <00fa454d-3a62-6282-89dd-d84005db9891@mrabarnett.plus.com>

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On 2016-05-10 23:36, DFS wrote:
[snip]
>
> If lists are still being created:
>
> * at every moment in time, len(list1) returns a length that doesn't
> change even if data is added to the list after the call to len().
>
> Example: If the list has 100 items in it at the point len(list) is called:
>
> for i in range(len(list1))
>
> will never iterate more than 100x, no matter how large list1 grows to.
>
> Caveat: since list1 may be bigger or smaller than the other lists at
> that moment in time, an error may occur when using list2[i], list3[i].
>
>
> Is that all correct as you understand it?
>
Yes.
>
>
> * at every moment in time, zip(list1, list2, etc) will return a fixed,
> same-length lists of tuples, which doesn't change even if data is added
> to any of the lists after the call to zip().
>
> Example: if the lists have 100, 97 and 102 items in them at the point
> zip(lists) is called:
>
> for item1, item2, item3 in zip(list1, list2, list3)
>
> will never iterate beyond 97x, even if the lists grow while the
> enumeration is occurring.
>
> Caveat: since zip() possibly truncates lists, the results - the usage of
> the data - could be completely invalid.
>
>
> Is that all correct as you understand it?
>
In Python 2, zip iterates through the arguments immediately and returns 
a list of tuples, so the answer is yes.

In Python 3, zip returns a lazy iterator (like itertools.izip in Python 
2) that gets the values from the arguments _on demand_, so the answer is no.

[snip]

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Thread

pylint woes DFS <nospam@dfs.com> - 2016-05-07 12:51 -0400
  Re: pylint woes Chris Angelico <rosuav@gmail.com> - 2016-05-08 03:01 +1000
    Re: pylint woes DFS <nospam@dfs.com> - 2016-05-07 21:16 -0400
      Re: pylint woes Chris Angelico <rosuav@gmail.com> - 2016-05-08 11:36 +1000
        Re: pylint woes DFS <nospam@dfs.com> - 2016-05-07 22:15 -0400
          Re: pylint woes Chris Angelico <rosuav@gmail.com> - 2016-05-08 12:50 +1000
            Re: pylint woes DFS <nospam@dfs.com> - 2016-05-10 18:36 -0400
              Re: pylint woes MRAB <python@mrabarnett.plus.com> - 2016-05-11 02:02 +0100
      Re: pylint woes Stephen Hansen <me+python@ixokai.io> - 2016-05-07 19:14 -0700
        Re: pylint woes DFS <nospam@dfs.com> - 2016-05-07 23:04 -0400
          Re: pylint woes Stephen Hansen <me+python@ixokai.io> - 2016-05-07 20:46 -0700
            Re: pylint woes DFS <nospam@dfs.com> - 2016-05-08 10:26 -0400
          Re: pylint woes Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-05-08 08:50 +0300
            Re: pylint woes DFS <nospam@dfs.com> - 2016-05-08 10:25 -0400
              Re: pylint woes Chris Angelico <rosuav@gmail.com> - 2016-05-09 00:36 +1000
                Re: pylint woes DFS <nospam@dfs.com> - 2016-05-08 11:06 -0400
                Re: pylint woes Stephen Hansen <me+python@ixokai.io> - 2016-05-08 08:15 -0700
                Re: pylint woes Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-05-09 13:17 +1200
                Re: pylint woes Chris Angelico <rosuav@gmail.com> - 2016-05-09 12:18 +1000
                Re: pylint woes DFS <nospam@dfs.com> - 2016-05-08 22:58 -0400
                Re: pylint woes Chris Angelico <rosuav@gmail.com> - 2016-05-09 01:15 +1000
                Re: pylint woes DFS <nospam@dfs.com> - 2016-05-08 17:06 -0400
              Re: pylint woes Stephen Hansen <me+python@ixokai.io> - 2016-05-08 08:11 -0700
              Re: pylint woes Steven D'Aprano <steve@pearwood.info> - 2016-05-09 01:51 +1000
                Re: pylint woes DFS <nospam@dfs.com> - 2016-05-08 17:04 -0400
                Re: pylint woes Steven D'Aprano <steve@pearwood.info> - 2016-05-09 13:09 +1000
      Re: pylint woes MRAB <python@mrabarnett.plus.com> - 2016-05-08 03:21 +0100
      Re: pylint woes Steven D'Aprano <steve@pearwood.info> - 2016-05-08 21:36 +1000
        Re: pylint woes DFS <nospam@dfs.com> - 2016-05-08 17:24 -0400
          Re: pylint woes Joel Goldstick <joel.goldstick@gmail.com> - 2016-05-08 17:39 -0400
          Re: pylint woes Steven D'Aprano <steve@pearwood.info> - 2016-05-09 13:46 +1000
  Re: pylint woes Michael Selik <michael.selik@gmail.com> - 2016-05-07 18:42 +0000
  Re: pylint woes Peter Pearson <pkpearson@nowhere.invalid> - 2016-05-07 18:43 +0000
    Re: pylint woes DFS <nospam@dfs.com> - 2016-05-08 17:05 -0400
  Re: pylint woes Christopher Reimer <christopher_reimer@icloud.com> - 2016-05-07 11:52 -0700
    Re: pylint woes DFS <nospam@dfs.com> - 2016-05-07 23:38 -0400
      Re: pylint woes Chris Angelico <rosuav@gmail.com> - 2016-05-08 13:56 +1000
      Re: pylint woes Peter Otten <__peter__@web.de> - 2016-05-08 16:19 +0200
  Re: pylint woes Stephen Hansen <me+python@ixokai.io> - 2016-05-07 12:21 -0700
  Re: pylint woes Stephen Hansen <me@ixokai.io> - 2016-05-07 12:23 -0700
  Re: pylint woes Terry Reedy <tjreedy@udel.edu> - 2016-05-07 15:40 -0400
    Re: pylint woes DFS <nospam@dfs.com> - 2016-05-07 23:28 -0400
      Re: pylint woes Chris Angelico <rosuav@gmail.com> - 2016-05-08 13:51 +1000
        Re: pylint woes DFS <nospam@dfs.com> - 2016-05-08 00:40 -0400
          Re: pylint woes Chris Angelico <rosuav@gmail.com> - 2016-05-08 14:55 +1000
      Re: pylint woes Stephen Hansen <me+python@ixokai.io> - 2016-05-07 20:55 -0700
      Re: pylint woes Ian Kelly <ian.g.kelly@gmail.com> - 2016-05-07 23:09 -0600
      Re: pylint woes Peter Otten <__peter__@web.de> - 2016-05-08 16:12 +0200
  Re: pylint woes Christopher Reimer <christopher_reimer@icloud.com> - 2016-05-07 12:43 -0700
  Re: pylint woes Ray Cote <rgacote@appropriatesolutions.com> - 2016-05-07 15:52 -0400
  Re: pylint woes Christopher Reimer <christopher_reimer@icloud.com> - 2016-05-07 13:20 -0700
  Re: pylint woes Chris Angelico <rosuav@gmail.com> - 2016-05-08 07:56 +1000
  Re: pylint woes Terry Reedy <tjreedy@udel.edu> - 2016-05-07 21:44 -0400
  Re: pylint woes Steven D'Aprano <steve@pearwood.info> - 2016-05-08 13:25 +1000
    Re: pylint woes DFS <nospam@dfs.com> - 2016-05-08 00:10 -0400
      Re: pylint woes Chris Angelico <rosuav@gmail.com> - 2016-05-08 14:21 +1000
      Re: pylint woes "D'Arcy J.M. Cain" <darcy@VybeNetworks.com> - 2016-05-08 08:50 -0400
      Re: pylint woes Chris Angelico <rosuav@gmail.com> - 2016-05-08 23:01 +1000
        Re: pylint woes Larry Hudson <orgnut@yahoo.com> - 2016-05-08 13:45 -0700
          Re: pylint woes Chris Angelico <rosuav@gmail.com> - 2016-05-09 08:07 +1000
            Re: pylint woes Larry Hudson <orgnut@yahoo.com> - 2016-05-08 18:28 -0700
        Re: pylint woes Dan Sommers <dan@tombstonezero.net> - 2016-05-08 20:49 +0000
          Re: pylint woes Chris Angelico <rosuav@gmail.com> - 2016-05-09 08:10 +1000
      Re: pylint woes Steven D'Aprano <steve@pearwood.info> - 2016-05-09 03:25 +1000
        Re: pylint woes DFS <nospam@dfs.com> - 2016-05-08 17:16 -0400
          Re: pylint woes Stephen Hansen <me+python@ixokai.io> - 2016-05-08 14:38 -0700
            Re: pylint woes DFS <nospam@dfs.com> - 2016-05-08 17:46 -0400
              Re: pylint woes Stephen Hansen <me+python@ixokai.io> - 2016-05-08 15:05 -0700
                Re: pylint woes DFS <nospam@dfs.com> - 2016-05-08 18:24 -0400

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