Re: Type of an object:

From	Gregory Ewing <greg.ewing@canterbury.ac.nz>
Newsgroups	comp.lang.python
Subject	Re: Type of an object:
Date	2013-12-19 00:39 +1300
Message-ID	<bhdfrdFjo0gU1@mid.individual.net> (permalink)
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Steven D'Aprano wrote:
> It's the *non-class* part I reckon is an accident, or a bug. Telling me 
> that weakproxy sets __class__ to a *class* doesn't argue for or against 
> me.

I wouldn't describe what weakref.proxy is doing as
*setting* __class__ to anything. Rather, it's arranging
things so that when you *get* x.__class__, it returns
something other than type(x). And I expect it's achieving
that effect by exploiting one of the general mechanisms
available for overriding attribute access.

You seem to think it's an "accident" that there is
no protection in place to prevent __class__ access from
being overridden in such a way that it returns something
other than a class.

I suppose you could say that this "works by accident", but
I would say that it simply works. There may not be any
obvious practical *use* for it, but it's not worth
anyone's time to go out of their way to prevent it.

-- 
Greg

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Type of an object: ‘obj.__class__’ versus ‘type(obj)’ Ben Finney <ben+python@benfinney.id.au> - 2013-12-16 12:51 +1100
  Re: Type of an object: ‘obj.__class__’ versus ‘type(obj)’ Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-12-16 22:17 +0000
    Re: Type of an object: ‘obj.__class__’ versus ‘type(obj)’ dieter <dieter@handshake.de> - 2013-12-17 08:14 +0100
      Re: Type of an object: ‘obj.__class__’ versus ‘type(obj)’ Steven D'Aprano <steve@pearwood.info> - 2013-12-17 07:42 +0000
        Re: Type of an object: Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2013-12-17 23:35 +1300
          Re: Type of an object: Ethan Furman <ethan@stoneleaf.us> - 2013-12-17 06:50 -0800
          Re: Type of an object: Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-12-17 15:08 +0000
            Re: Type of an object: Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2013-12-18 11:15 +1300
              Re: Type of an object: Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-12-17 23:51 +0000
                Re: Type of an object: Ethan Furman <ethan@stoneleaf.us> - 2013-12-17 17:10 -0800
                Re: Type of an object: Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2013-12-19 00:45 +1300
                Re: Type of an object: Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2013-12-19 00:39 +1300

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