[ python-Bugs-1263635 ] type() and isinstance() do not call __getattribute__

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Bugs item #1263635, was opened at 2005-08-19 02:07
Message generated for change (Comment added) made by gbrandl
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Category: Python Interpreter Core
Group: Python 2.4
>Status: Closed
>Resolution: Wont Fix
Priority: 5
Submitted By: Per Vognsen (pervognsen)
Assigned to: Nobody/Anonymous (nobody)
Summary: type() and isinstance() do not call __getattribute__

Initial Comment:
The built-in functions type() and isinstance() do not call 
__getattribute__ for instances of user-defined classes. 
Thus, for instance,

x.__class__ == sometype

and

type(x) == sometype

can give inconsistent results.

I ran into this problem in writing a transparent 
persistence system, where instances of proxy classes 
are used as stand-ins for unloaded objects and the 
proxy does just-in-time loading by overloading 
__getattribute__ and __setattr__ (which changes 
__class__).

(This applies to 2.4.1.)

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>Comment By: Georg Brandl (gbrandl)
Date: 2006-02-20 22:10

Message:
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Closing as I feel Raymond's right.

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Comment By: Raymond Hettinger (rhettinger)
Date: 2005-08-26 08:48

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I don't think this is going to change.  A number of builtins
directly access an object's structure and do not respect
overrides via __getattribute__.  This is somewhat intrinsic
the Python's current design.

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