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Re: __dict__ attribute for built-in types

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On 10/27/2011 6:52 PM, candide wrote:

> No but I'm expecting from Python documentation to mention the laws of
> Python ...

The details of CPython builtin classes are not laws of Python. It *is* a 
'law of Python' that classes can use 'slots = ' to restrict the 
attributes of instances. By implication, builtin classes in any 
implementation do not have to allow attribute assignment. I do not 
believe it would be a violation if some implementation did so.

None of this is to say that we could not say something on the subject at 
the beginning of the 'built-in types' chapter of the lib manual.

> OK but I'm talking about classes, not instances :

Yes you are. The class determines whether its instances have assignable 
new attributes.

 > 42 has no __dict__ > attribute but,
 > may be, 43 _has_ such attribute, who knows in advance ? ;)

True, in a sense, but if the class allowed a user to execute
"42.__dict__ = {}" then you could safely assume that "43.xxx = z" should 
work also.

-- 
Terry Jan Reedy

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__dict__ attribute for built-in types candide <candide@free.invalid> - 2011-10-27 12:08 +0200
  Re: __dict__ attribute for built-in types Arnaud Delobelle <arnodel@gmail.com> - 2011-10-27 11:36 +0100
  Re: __dict__ attribute for built-in types Duncan Booth <duncan.booth@invalid.invalid> - 2011-10-27 11:03 +0000
    Re: __dict__ attribute for built-in types Chris Angelico <rosuav@gmail.com> - 2011-10-28 00:25 +1100
      Re: __dict__ attribute for built-in types Duncan Booth <duncan.booth@invalid.invalid> - 2011-10-27 14:36 +0000
        Re: __dict__ attribute for built-in types Chris Angelico <rosuav@gmail.com> - 2011-10-28 09:39 +1100
    Re: __dict__ attribute for built-in types candide <candide@free.invalid> - 2011-10-27 16:01 +0200
      Re: __dict__ attribute for built-in types Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-10-27 22:19 +0000
        Re: __dict__ attribute for built-in types candide <candide@free.invalid> - 2011-10-28 00:52 +0200
          Re: __dict__ attribute for built-in types Terry Reedy <tjreedy@udel.edu> - 2011-10-27 22:44 -0400
          Re: __dict__ attribute for built-in types alex23 <wuwei23@gmail.com> - 2011-10-27 19:48 -0700
          Re: __dict__ attribute for built-in types Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-10-28 08:01 +0000
            Re: __dict__ attribute for built-in types candide <candide@free.invalid> - 2011-10-28 12:03 +0200
            Re: __dict__ attribute for built-in types Christian Heimes <lists@cheimes.de> - 2011-10-28 13:51 +0200
          Re: __dict__ attribute for built-in types Peter Pearson <ppearson@nowhere.invalid> - 2011-10-28 15:52 +0000
      Re: __dict__ attribute for built-in types Hrvoje Niksic <hniksic@xemacs.org> - 2011-10-28 00:57 +0200
        Re: __dict__ attribute for built-in types candide <candide@free.invalid> - 2011-10-28 01:36 +0200
          Re: __dict__ attribute for built-in types MRAB <python@mrabarnett.plus.com> - 2011-10-28 01:02 +0100
            Re: __dict__ attribute for built-in types candide <candide@free.invalid> - 2011-10-28 04:46 +0200
              Re: __dict__ attribute for built-in types Patrick Maupin <pmaupin@gmail.com> - 2011-10-27 20:02 -0700
                Re: __dict__ attribute for built-in types candide <candide@free.invalid> - 2011-10-28 12:04 +0200
          Re: __dict__ attribute for built-in types Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-10-28 06:21 +0000
          Re: __dict__ attribute for built-in types Hrvoje Niksic <hniksic@xemacs.org> - 2011-10-28 11:08 +0200
            Re: __dict__ attribute for built-in types candide <candide@free.invalid> - 2011-10-28 12:23 +0200
  Re: __dict__ attribute for built-in types Nobody <nobody@nowhere.com> - 2011-10-28 06:49 +0100

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