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Re: meaning of: line, =

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From Devin Jeanpierre <jeanpierreda@gmail.com>
Date Thu, 5 Feb 2015 01:10:09 -0800
Subject Re: meaning of: line, =
To Chris Angelico <rosuav@gmail.com>
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On Wed, Feb 4, 2015 at 1:18 PM, Chris Angelico <rosuav@gmail.com> wrote:
> On Thu, Feb 5, 2015 at 4:36 AM, Peter Otten <__peter__@web.de> wrote:
>> Another alternative is to put a list literal on the lefthand side:
>>
>>>>> def f(): yield 42
>>
>> ...
>>>>> [result] = f()
>>>>> result
>> 42
>
> Huh, was not aware of that alternate syntax.

Nor are most people. Nor is Python, in some places -- it seems like
people forgot about it when writing some bits of the grammar.

I'd suggest not using it.

>> (If you're worried: neither the list nor the tuple will be created; the
>> bytecode is identical in both cases)
>
> It can't possibly be created anyway. Python doesn't have a notion of
> "assignable thing that, when assigned to, will assign to something
> else" like C's pointers or C++'s references. There's nothing that you
> could put into the list that would have this behaviour.

C pointers don't do that either. It's really just references. (C
pointers aren't any more action-at-a-distance than Python attributes.)

Anyway, it could create a new list in Python, because Python can do
whatever it wants. But it doesn't, because as you say, that wouldn't
do anything.

-- Devin

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Thread

Re: meaning of: line, = Albert-Jan Roskam <fomcl@yahoo.com> - 2015-02-04 14:38 +0000
  Re: meaning of: line, = Rustom Mody <rustompmody@gmail.com> - 2015-02-04 07:09 -0800
    Re: meaning of: line, = Peter Otten <__peter__@web.de> - 2015-02-04 18:36 +0100
    Re: meaning of: line, = Chris Angelico <rosuav@gmail.com> - 2015-02-05 08:18 +1100
    Re: meaning of: line, = Devin Jeanpierre <jeanpierreda@gmail.com> - 2015-02-05 01:10 -0800
      Re: meaning of: line, = Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-02-05 20:40 +1100
        Re: meaning of: line, = Ian Kelly <ian.g.kelly@gmail.com> - 2015-02-05 09:08 -0700
          Re: meaning of: line, = Rustom Mody <rustompmody@gmail.com> - 2015-02-05 08:45 -0800
            Re: meaning of: line, = Skip Montanaro <skip.montanaro@gmail.com> - 2015-02-05 10:56 -0600
            Re: meaning of: line, = Tim Chase <python.list@tim.thechases.com> - 2015-02-05 11:00 -0600
            Re: meaning of: line, = Rustom Mody <rustompmody@gmail.com> - 2015-02-05 08:59 -0800
              Re: meaning of: line, = Devin Jeanpierre <jeanpierreda@gmail.com> - 2015-02-06 05:09 -0800
                Re: meaning of: line, = Rustom Mody <rustompmody@gmail.com> - 2015-02-06 05:20 -0800
                Re: meaning of: line, = Rustom Mody <rustompmody@gmail.com> - 2015-02-06 06:03 -0800
        Re: meaning of: line, = Tim Chase <python.list@tim.thechases.com> - 2015-02-05 10:21 -0600
        Re: meaning of: line, = Devin Jeanpierre <jeanpierreda@gmail.com> - 2015-02-05 17:12 -0800
        Re: meaning of: line, = Chris Angelico <rosuav@gmail.com> - 2015-02-06 12:17 +1100
          Re: meaning of: line, = Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-02-06 17:52 +1300
      Re: meaning of: line, = Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-02-06 12:30 +1300

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