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Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers?

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On 12/4/2013 3:07 PM, Piotr Dobrogost wrote:

You have proposed to make non-identifier attribute names 'official', 
rather than discouraged, by abbreviating
 > x = getattr(obj, 'value-1')
or
x = obj.__dict__['value-1']  # implementation detail
as
> x = obj.'value-1'

The discussion of enlarging the scope of 'identifier' is not relevant as 
you are not proposing that. In particular, you are not asking that 
obj.value-1 get the 'value-1' attribute of obj. The discussion of 
keystrokes is also a side-track.

What you are proposing, I believe, is a new grammatical category: 
attribute-name := identifier or string-literal. This would break the 
symmetry of the grammatical form identifier '.' identifier and change it 
to the asymmetrical identifier '.' attribute-name, and that is the 
problem.  Most identifiers are attributes of a namespace and many 
attributes are set *and accessed* as undotted names in module or class 
code.  The symmetry is at least partly inherent and breaking it does not 
work very well.

 >>> len is __builtins__.len
True
 >>> __globals__ = __import__(__name__)
 >>> a = 1
 >>> a is __globals__.a
True

To put it another way, how does 'obj' get the non-standard attribute 
'value-1', when obj is a module or class? The workaround given above for 
module attributes will not work for classes.

>> Remember the Python philosophy that there ought to be one way to do
>> it.
>
> Funny you use this argument against my idea as this idea comes from
> following this rule whereas getattr goes against it.

Not really. As others have pointed out, getattr is the preferred way to 
get the value of an attribute when you have an object with attributes 
and a run-time-only reference to the name in a string variable.

It would also be the case that "obj.'value' is obj.value", so the 
proposal *would* add duplication.

-- 
Terry Jan Reedy

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Thread

Why is there no natural syntax for accessing attributes with names not being valid identifiers? Piotr Dobrogost <p@google-groups-2013.dobrogost.net> - 2013-12-03 09:14 -0800
  Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Ned Batchelder <ned@nedbatchelder.com> - 2013-12-03 12:38 -0500
  Re: Why is there no natural syntax for accessing attributes with names
 not being valid identifiers? Dave Angel <davea@davea.name> - 2013-12-03 12:48 -0500
    Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Piotr Dobrogost <p@google-groups-2013.dobrogost.net> - 2013-12-04 14:05 -0800
      Re: Why is there no natural syntax for accessing attributes with
 names not being valid identifiers? Dave Angel <davea@davea.name> - 2013-12-04 17:28 -0500
  Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Ethan Furman <ethan@stoneleaf.us> - 2013-12-03 09:31 -0800
    Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Piotr Dobrogost <p@google-groups-2013.dobrogost.net> - 2013-12-03 15:49 -0800
  Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? random832@fastmail.us - 2013-12-03 13:03 -0500
    Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Piotr Dobrogost <p@google-groups-2013.dobrogost.net> - 2013-12-03 15:47 -0800
      Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Tim Chase <python.list@tim.thechases.com> - 2013-12-03 19:06 -0600
        Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Piotr Dobrogost <p@google-groups-2013.dobrogost.net> - 2013-12-04 12:35 -0800
          Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-12-04 20:46 +0000
          Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Jerry Hill <malaclypse2@gmail.com> - 2013-12-04 15:58 -0500
          Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Ethan Furman <ethan@stoneleaf.us> - 2013-12-04 13:02 -0800
          Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Neil Cerutti <neilc@norwich.edu> - 2013-12-04 21:41 +0000
            Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Piotr Dobrogost <p@google-groups-2013.dobrogost.net> - 2013-12-04 13:54 -0800
              Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Neil Cerutti <neilc@norwich.edu> - 2013-12-06 14:07 +0000
                Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Piotr Dobrogost <p@google-groups-2013.dobrogost.net> - 2013-12-06 08:51 -0800
                Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Rotwang <sg552@hotmail.co.uk> - 2013-12-07 00:47 +0000
            Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Piotr Dobrogost <p@google-groups-2013.dobrogost.net> - 2013-12-04 14:13 -0800
              Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Ethan Furman <ethan@stoneleaf.us> - 2013-12-04 15:09 -0800
                Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Piotr Dobrogost <p@google-groups-2013.dobrogost.net> - 2013-12-04 15:57 -0800
                Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Ethan Furman <ethan@stoneleaf.us> - 2013-12-04 16:26 -0800
                Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Ned Batchelder <ned@nedbatchelder.com> - 2013-12-04 20:17 -0500
          Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Terry Reedy <tjreedy@udel.edu> - 2013-12-04 21:58 -0500
          Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Ethan Furman <ethan@stoneleaf.us> - 2013-12-04 19:05 -0800
          Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Steven D'Aprano <steve@pearwood.info> - 2013-12-05 07:56 +0000
      Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Tim Roberts <timr@probo.com> - 2013-12-03 21:45 -0800
        Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? rusi <rustompmody@gmail.com> - 2013-12-03 22:31 -0800
          Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Ian Kelly <ian.g.kelly@gmail.com> - 2013-12-04 01:57 -0700
            Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? rusi <rustompmody@gmail.com> - 2013-12-04 02:09 -0800
              Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-12-04 11:29 +0100
                Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? rusi <rustompmody@gmail.com> - 2013-12-04 04:01 -0800
                Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-12-04 13:32 +0100
                Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? rusi <rustompmody@gmail.com> - 2013-12-04 05:02 -0800
                Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-12-04 20:57 +0100
              Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Chris Angelico <rosuav@gmail.com> - 2013-12-04 21:33 +1100
                Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? rusi <rustompmody@gmail.com> - 2013-12-04 03:27 -0800
              Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Tim Chase <python.list@tim.thechases.com> - 2013-12-04 05:25 -0600
              Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2013-12-04 13:30 +0200
                Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Chris Angelico <rosuav@gmail.com> - 2013-12-04 22:40 +1100
                Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Ethan Furman <ethan@stoneleaf.us> - 2013-12-04 07:56 -0800
              Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Ian Kelly <ian.g.kelly@gmail.com> - 2013-12-04 19:43 -0700
                Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? rusi <rustompmody@gmail.com> - 2013-12-04 20:48 -0800
          Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-12-04 19:27 -0500
            Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Roy Smith <roy@panix.com> - 2013-12-04 20:03 -0500
        Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Ethan Furman <ethan@stoneleaf.us> - 2013-12-04 01:12 -0800
        Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Roy Smith <roy@panix.com> - 2013-12-04 08:23 -0500
          Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Piotr Dobrogost <p@google-groups-2013.dobrogost.net> - 2013-12-04 13:00 -0800
        Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Piotr Dobrogost <p@google-groups-2013.dobrogost.net> - 2013-12-04 12:07 -0800
          Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Ethan Furman <ethan@stoneleaf.us> - 2013-12-04 12:22 -0800
          Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-12-04 20:55 +0000
          Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Ethan Furman <ethan@stoneleaf.us> - 2013-12-04 13:00 -0800
          Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Terry Reedy <tjreedy@udel.edu> - 2013-12-04 17:11 -0500
            Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Piotr Dobrogost <p@google-groups-2013.dobrogost.net> - 2013-12-04 15:42 -0800
              Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Terry Reedy <tjreedy@udel.edu> - 2013-12-04 22:21 -0500
          Re: Why is there no natural syntax for accessing attributes with names not being valid identifiers? Rotwang <sg552@hotmail.co.uk> - 2013-12-05 01:50 +0000

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