Bugs item #1170766, was opened at 2005-03-25 16:54
Message generated for change (Settings changed) made by rhettinger
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Category: Python Library
Group: Python 2.4
Status: Open
Resolution: None
>Priority: 6
Submitted By: Alexander Kozlovsky (kozlovsky)
Assigned to: Nobody/Anonymous (nobody)
Summary: weakref.proxy incorrect behaviour
Initial Comment:
According documentation, proxy in most contexts must
have the same behaviour as object itself.
PROBLEM:
bool(proxy_object) != bool(object_itself)
EXAMPLE:
>>> class X(list): pass # collection class
...
>>> x = X() # empty collection
>>> import weakref
>>> proxy = weakref.proxy(x)
>>> bool(x)
False
>>> bool(proxy)
True
PYTHON VERSION:
2.4 (#60, Nov 30 2004, 11:49:19) [MSC v.1310 32 bit
(Intel)]
also tested on:
2.3.4 (#53, May 25 2004, 21:17:02) [MSC v.1200 32 bit
(Intel)]
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Comment By: Michael Hudson (mwh)
Date: 2005-03-29 08:39
Message:
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Also see bug #1075356 (which is very minor, but might as
well get fixed at the same time).
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Comment By: Armin Rigo (arigo)
Date: 2005-03-29 08:23
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The following type slots appear to be missing in the proxy types:
* nb_(inplace_){floor,true}_divide
* sq_repeat, sq_concat, sq_item, sq_ass_item, sq_inplace_concat,
sq_inplace_repeat (which are needed for operator.repeat(), operator.concat(),
etc. to work)
* tp_as_buffer
* tp_richcompare (tp_compare alone is not enough)
* tp_descr_get, tp_descr_set (for proxies to descriptors...)
* nb_coerce (though it seems that only an explicit call to coerce() can show
that this is missing; implicit coercion is done correctly in other operators)
* nb_oct, nb_hex
As far as I can tell, there is no existing operator that is broken in the same
way that nb_nonzero was.
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Comment By: Raymond Hettinger (rhettinger)
Date: 2005-03-27 06:17
Message:
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Fixed the __nonzero__ problem for Py2.5 and will backport to
Py2.4. See Objects/weakrefobject.c 1.21.
Leaviing this report open until the rest of the module can
be checked and fixed.
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Comment By: Armin Rigo (arigo)
Date: 2005-03-26 09:50
Message:
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The bug is in weakrefobject:proxy_nonzero(), which calls the underlying
object's nb_nonzero slot instead of going through the general PyObject_IsTrue()
mecanism. Built-in types like list and dict don't have a nb_nonzero slot.
As a related bug, (Callable)ProxyType should implement tp_richcompare in
addition to tp_compare. In fact, we should review the code to check if
ProxyType knows about the most recent type slots...
----------------------------------------------------------------------
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