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Re: Syntactic sugar for assignment statements: one value to multiple targets?

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On 08/03/2011 03:36 AM, Katriel Cohn-Gordon wrote:
> On Wed, Aug 3, 2011 at 9:25 AM, Steven D'Aprano wrote:
>> a, b, c, d, e = [dict() for i in range(5)]
>
> I think this is good code -- if you want five different dicts,
> then you should call dict five times. Otherwise Python will
> magically call your expression more than once, which isn't
> very nice. And what if your datatype constructor has
> side-effects?

If the side-effects are correct behavior (perhaps opening files, 
network connections, or even updating a class variable) then 
constructor side-effects are just doing what they're supposed to. 
  E.g. something I use somewhat regularly in my code[*]:

  a,b,c,d = (file('file%i.txt', 'w') for i in range(4))

If the side-effects aren't performing the correct behavior, fix 
the constructor. :)

-tkc


[*] okay, it's more like

(features,
  adjustments,
  internet,
  ) = (file(fname) for fname in (
    'features.txt',
    'adjustments.txt',
    'internet.txt'
    )

or even

(features,
  adjustments,
  internet,
  ) = (
    set(
      line.strip().upper()
      for line
      in file(fname)
      if line.strip()
      )
    for fname in (
    'features.txt',
    'adjustments.txt',
    'internet.txt'
    )

to load various set() data from text-files.

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Syntactic sugar for assignment statements: one value to multiple targets? gc <gc1223@gmail.com> - 2011-08-02 18:45 -0700
  Re: Syntactic sugar for assignment statements: one value to multiple targets? Chris Angelico <rosuav@gmail.com> - 2011-08-03 03:09 +0100
  Re: Syntactic sugar for assignment statements: one value to multiple targets? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-08-03 18:25 +1000
    Re: Syntactic sugar for assignment statements: one value to multiple targets? Tim Chase <python.list@tim.thechases.com> - 2011-08-03 06:15 -0500
    Re: Syntactic sugar for assignment statements: one value to multiple targets? Tim Chase <python.list@tim.thechases.com> - 2011-08-03 06:25 -0500
      Re: Syntactic sugar for assignment statements: one value to multiple targets? gc <gc1223@gmail.com> - 2011-08-16 12:50 -0700
  Re: Syntactic sugar for assignment statements: one value to multiple targets? Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2011-08-03 20:29 +1200
  Re: Syntactic sugar for assignment statements: one value to multiple targets? "Martin P. Hellwig" <martin.hellwig@gmail.com> - 2011-08-16 21:39 +0100
    Re: Syntactic sugar for assignment statements: one value to multiple targets? gc <gc1223@gmail.com> - 2011-08-16 17:14 -0700
      Re: Syntactic sugar for assignment statements: one value to multiple targets? MRAB <python@mrabarnett.plus.com> - 2011-08-17 03:11 +0100
      Re: Syntactic sugar for assignment statements: one value to multiple targets? Chris Angelico <rosuav@gmail.com> - 2011-08-17 08:13 +0100
        Re: Syntactic sugar for assignment statements: one value to multiple targets? gc <gc1223@gmail.com> - 2011-08-17 02:26 -0700
          Re: Syntactic sugar for assignment statements: one value to multiple targets? Chris Angelico <rosuav@gmail.com> - 2011-08-17 10:45 +0100
            Re: Syntactic sugar for assignment statements: one value to multiple targets? gc <gc1223@gmail.com> - 2011-08-17 03:33 -0700
          Re: Syntactic sugar for assignment statements: one value to multiple targets? Terry Reedy <tjreedy@udel.edu> - 2011-08-17 12:12 -0400
          Re: Syntactic sugar for assignment statements: one value to multiple targets? MRAB <python@mrabarnett.plus.com> - 2011-08-17 17:55 +0100
          Re: Syntactic sugar for assignment statements: one value to multiple targets? Chris Angelico <rosuav@gmail.com> - 2011-08-17 18:25 +0100
          Re: Syntactic sugar for assignment statements: one value to multiple targets? "OKB (not okblacke)" <brenNOSPAMbarn@NObrenSPAMbarn.net> - 2011-08-17 19:13 +0000
      Re: Syntactic sugar for assignment statements: one value to multiple targets? Zero Piraeus <schesis@gmail.com> - 2011-08-17 16:07 -0400
  Re: Syntactic sugar for assignment statements: one value to multiple targets? Ethan Furman <ethan@stoneleaf.us> - 2011-08-17 12:52 -0700
  Re: Syntactic sugar for assignment statements: one value to multiple targets? John Pinner <funthyme@gmail.com> - 2011-08-18 02:26 -0700
  Re: Syntactic sugar for assignment statements: one value to multiple targets? Roy Smith <roy@panix.com> - 2011-08-18 09:13 -0400

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