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Re: meaning of: line, =

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From Devin Jeanpierre <jeanpierreda@gmail.com>
Date Thu, 5 Feb 2015 17:12:17 -0800
Subject Re: meaning of: line, =
To Ian Kelly <ian.g.kelly@gmail.com>
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On Thu, Feb 5, 2015 at 8:08 AM, Ian Kelly <ian.g.kelly@gmail.com> wrote:
> On Thu, Feb 5, 2015 at 2:40 AM, Steven D'Aprano
> <steve+comp.lang.python@pearwood.info> wrote:
>> Devin Jeanpierre wrote:
>>> On Wed, Feb 4, 2015 at 1:18 PM, Chris Angelico <rosuav@gmail.com> wrote:
>>>>>>>> [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.
>>
>> Got an example where you can use a,b but not [a,b] or (a,b)?
>
>>>> def f(a, (b, c)):
> ...     print a, b, c
> ...
>>>> f(3, [4, 5])
> 3 4 5
>>>> def g(a, [b, c]):
>   File "<stdin>", line 1
>     def g(a, [b, c]):
>              ^
> SyntaxError: invalid syntax
>
> Although to be fair, the first syntax there is no longer valid either
> in Python 3.

As Ian rightly understood, I was referring to differences between "[a,
b, ...]" and "(a, b, ...)".

Here's another example, one that still exists in Python 3:

>>> [] = ''
>>> () = ''
  File "<stdin>", line 1
SyntaxError: can't assign to ()

The syntax explicitly blacklists (), but forgets to blacklist [].

-- Devin

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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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