The oddity is that calling `__reduce_ex__` on the instance is fine, but on
the class it is not. When serialising a declarative class it finds itself
serialising the class type, which fails. This actually fails for the
`object`, too (see below).
So I think what's happening is that serialisation fails because
`_sa_instance_state`
(somewhere inside it) contains a class. This is probably a yaml bug, then.
In [1]: object().__reduce_ex__(2)
Out[1]: (<function copy_reg.__newobj__>, (object,), None, None, None)
In [2]: object.__reduce_ex__(2)
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-1-eebec0cadfee> in <module>()
----> 1 object.__reduce_ex__(2)
/usr/lib/python2.7/copy_reg.pyc in _reduce_ex(self, proto)
68 else:
69 if base is self.__class__:
---> 70 raise TypeError, "can't pickle %s objects" %
base.__name__
71 state = base(self)
72 args = (self.__class__, base, state)
TypeError: can't pickle int objects
On 24 October 2014 17:55, Jonathan Vanasco <jvana...@gmail.com> wrote:
>
> On Friday, October 24, 2014 10:39:43 AM UTC-4, Peter Waller wrote:
>>
>> I was also hoping to "just use yaml" to avoid writing custom dumping
>> code, since it seems in general like a useful capability. So I may yet try
>> and find the underlying bug and fix it.
>>
>
> It might not be a bug, and the effect of an "implementation feature" of
> SqlAlchemy. I tried (naively) playing around with your example, and
> thought back to how SqlAlchemy accomplishes much of it's magic by creating
> custom comparators (and other private methods) on the classes and columns.
>
> Playing around with it, the problem seems to be with the SqlAlchemy
> object's __reduce_ex__ method. If you simply use __reduce__ in yaml, it
> works. I couldn't figure out what Foo inherits __reduce_ex__ from , or if
> any of the columns have it.
>
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