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Re: zip as iterator and bad/good practices

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Date Sat, 13 Jun 2015 10:26:49 +1000
Subject Re: zip as iterator and bad/good practices
From Chris Angelico <rosuav@gmail.com>
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On Sat, Jun 13, 2015 at 10:02 AM,  <sohcahtoa82@gmail.com> wrote:
>>  >>> ints = [0, 1, 2, 2, 1, 4, 6, 5, 5]
>>  >>> ints[:] = [i for i in ints if not i % 2]
>>  >>> ints
>> [0, 2, 2, 4, 6]
>>
>>
>> --
>> Terry Jan Reedy
>
> On the second line of your final solution, is there any reason you're using `ints[:]` rather than just `ints`?

If you use "ints = [...]", it rebinds the name ints to the new list.
If you use "ints[:] = [...]", it replaces the entire contents of the
list with the new list. The two are fairly similar if there are no
other references to that list, but the replacement matches the
mutation behaviour of remove().

def just_some(ints):
    ints[:] = [i for i in ints if not i % 2]

ChrisA

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zip as iterator and bad/good practices Fabien <fabien.maussion@gmail.com> - 2015-06-12 17:00 +0200
  Re: zip as iterator and bad/good practices Fabien <fabien.maussion@gmail.com> - 2015-06-12 17:05 +0200
  Re: zip as iterator and bad/good practices Ian Kelly <ian.g.kelly@gmail.com> - 2015-06-12 09:26 -0600
    Re: zip as iterator and bad/good practices Fabien <fabien.maussion@gmail.com> - 2015-06-12 17:34 +0200
    Re: zip as iterator and bad/good practices Fabien <fabien.maussion@gmail.com> - 2015-06-12 17:59 +0200
  Re: zip as iterator and bad/good practices Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-06-12 17:22 +0100
  Re: zip as iterator and bad/good practices Laura Creighton <lac@openend.se> - 2015-06-12 22:34 +0200
  Re: zip as iterator and bad/good practices Terry Reedy <tjreedy@udel.edu> - 2015-06-12 19:27 -0400
  Re: zip as iterator and bad/good practices Terry Reedy <tjreedy@udel.edu> - 2015-06-12 19:43 -0400
    Re: zip as iterator and bad/good practices sohcahtoa82@gmail.com - 2015-06-12 17:02 -0700
      Re: zip as iterator and bad/good practices Chris Angelico <rosuav@gmail.com> - 2015-06-13 10:26 +1000
        Re: zip as iterator and bad/good practices sohcahtoa82@gmail.com - 2015-06-12 17:39 -0700
  Re: zip as iterator and bad/good practices jimages <jimages123@gmail.com> - 2015-06-13 13:32 +0800
    Re: zip as iterator and bad/good practices Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-06-13 07:17 +0000
      Re: zip as iterator and bad/good practices Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2015-06-13 13:48 +0100
        Re: zip as iterator and bad/good practices Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-06-13 16:16 +0000

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