[Anthony Baxter]
>> Ok, so here's the state of play: 2.3.5 is currently aimed for next
>> Tuesday, but there's an outstanding issue - the new copy code appears
>> to have broken something, see www.python.org/sf/1114776 for the gory
>> details.
...
[Alex Martelli]
> The problem boils down to: deepcopying an instance of a type that
> doesn't have an __mro__ (and is not one of the many types explicitly
> recorded in the _deepcopy_dispatch dictionary, such as types.ClassType,
> types.InstanceType, etc, etc).
>
> The easy fix: instead of cls.__mro__ use inspect.getmro which deals
> with that specifically.
>
> Before I commit the fix: can anybody help out with an example of a type
> anywhere in the standard library that should be deepcopyable, used to
> be deepcopyable in 2.3.4, isn't one of those which get explicitly
> recorded in copy._deepcopy_dispatch, AND doesn't have an __mro__? Even
> the _testcapi.Copyable type magically grows an __mro__; I'm not sure
> how to MAKE a type w/o one...
Since the original bug report came from Zopeland, chances are good
(although the report is too vague to be sure) that the problem
involves ExtensionClass. That's complicated C code in Zope predating
new-style classes, making it possible to build Python-class-like
objects in C code under old Pythons. In general, EC-derived classes
don't play well with newer Python features (well, at least not until
Zope 2.8, where ExtensionClass is recoded as a new-style Python class
-- but still keeping some semantics from old-style classes ... ).
Anyway, I expect that instances of any EC-derived class would have the
problem in the bug report. For example, the base Persistent class in
ZODB 3.2.5 is an ExtensionClass:
$ \python23\python.exe
Python 2.3.5c1 (#61, Jan 25 2005, 19:52:06) [MSC v.1200 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import ZODB # don't ask -- it's necessary to import this first
>>> from Persistence import Persistent
>>> p = Persistent()
>>> import copy
>>> copy.deepcopy(p) # deepcopy() barfs on __mro__
Traceback (most recent call last):
File "<stdin>", line 1, in ?
File "C:\Python23\lib\copy.py", line 200, in deepcopy
copier = _getspecial(cls, "__deepcopy__")
File "C:\Python23\lib\copy.py", line 66, in _getspecial
for basecls in cls.__mro__:
AttributeError: __mro__
>>> copy.copy(p) # copy() does too
Traceback (most recent call last):
File "<stdin>", line 1, in ?
File "C:\Python23\lib\copy.py", line 86, in copy
copier = _getspecial(cls, "__copy__")
File "C:\Python23\lib\copy.py", line 66, in _getspecial
for basecls in cls.__mro__:
AttributeError: __mro__
Unsure whether this is enough, but at least inspect.getmro() isn't
phased by an EC-derived class:
>>> inspect.getmro(Persistent)
(<extension class Persistence.Persistent at 100040D8>,)
More info from the bug report filer is really needed. A problem is
that this stuff doesn't appear "to work" under Python 2.3.4 either:
$ ../Python-2.3.4/python
Python 2.3.4 (#1, Aug 9 2004, 17:15:36)
[GCC 3.2.2 20030222 (Red Hat Linux 3.2.2-5)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import ZODB
>>> from Persistence import Persistent
>>> p = Persistent()
>>> import copy
>>> copy.deepcopy(p)
Traceback (most recent call last):
File "<stdin>", line 1, in ?
File "/home/tim/Python-2.3.4/Lib/copy.py", line 206, in deepcopy
y = _reconstruct(x, rv, 1, memo)
File "/home/tim/Python-2.3.4/Lib/copy.py", line 338, in _reconstruct
y = callable(*args)
TypeError: ExtensionClass object argument after * must be a sequence
>>> copy.copy(p)
Traceback (most recent call last):
File "<stdin>", line 1, in ?
File "/home/tim/Python-2.3.4/Lib/copy.py", line 95, in copy
return _reconstruct(x, rv, 0)
File "/home/tim/Python-2.3.4/Lib/copy.py", line 338, in _reconstruct
y = callable(*args)
TypeError: ExtensionClass object argument after * must be a sequence
>>>
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