[jira] [Resolved] (IMPALA-11974) Fix range/xrange/map/filter/ifilter/zip/izip issues regarding iterators being lazy

["Joe McDonnell (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IMPALA-11974?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Joe McDonnell resolved IMPALA-11974.
------------------------------------
    Fix Version/s: Impala 4.3.0
         Assignee: Joe McDonnell
       Resolution: Fixed

> Fix range/xrange/map/filter/ifilter/zip/izip issues regarding iterators being lazy
> ----------------------------------------------------------------------------------
>
>                 Key: IMPALA-11974
>                 URL: https://issues.apache.org/jira/browse/IMPALA-11974
>             Project: IMPALA
>          Issue Type: Sub-task
>          Components: Infrastructure
>    Affects Versions: Impala 4.3.0
>            Reporter: Joe McDonnell
>            Assignee: Joe McDonnell
>            Priority: Major
>             Fix For: Impala 4.3.0
>
>
> Python 3 made map, range, zip, and filter lazy. That means that existing Python code that relies on this turning into a list immediately need adjustments:
> {noformat}
> # Python 2:
> range(5) == [0,1,2,3,4]
> True
> # Python 3:
> range(5) == [0,1,2,3,4]
> False
> # Python 3 fix:
> list(range(5)) == [0,1,2,3,4]
> True
> # Same deal with map, zip, filter, etc.{noformat}
> This example is basic, but this applies across the board. 
> Since the ordinary operators like range, filter, etc are now lazy, the old lazy ones have been removed (xrange, ifilter, izip). Those need to be replaced, and the future package provides implementations of range, zip, map, filter, etc.
> See:
> [https://python-future.org/compatible_idioms.html#xrange]
> [https://python-future.org/compatible_idioms.html#range]
> [https://python-future.org/compatible_idioms.html#map]
> [https://python-future.org/compatible_idioms.html#imap]
> etc
> This corresponds to these pylint checks:
> xrange-builtin
> range-builtin-not-iterating
> map-builtin-not-iterating
> zip-builtin-not-iterating
> filter-builtin-not-iterating
> reduce-builtin
> deprecated-itertools-function
> Futurize has some tools to help:
> libfuturize.fixes.fix_xrange_with_import
> lib2to3.fixes.fix_map
> lib2to3.fixes.fix_filter



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