Fell into the same trap.
entities = query.fetch(batch_size)
File
"/home/kamel/Library/google_appengine/google/appengine/ext/db/__init__.py",
line 2157, in fetch
return list(self.run(limit=limit, offset=offset, **kwargs))
File
"/home/kamel/Library/google_appengine/google/appengine/ext/db/__init__.py",
line 2326, in next
return self.__model_class.from_entity(self.__iterator.next())
File
"/home/kamel/Library/google_appengine/google/appengine/ext/db/__init__.py",
line 1435, in from_entity
entity_values = cls._load_entity_values(entity)
File
"/home/kamel/Library/google_appengine/google/appengine/ext/db/__init__.py",
line 1413, in _load_entity_values
value = prop.make_value_from_datastore(value)
File "/home/kamel/labola/src/model/properties.py", line 295, in
make_value_from_datastore
return pickle.loads(value)
File "/usr/lib/python2.7/pickle.py", line 1382, in loads
return Unpickler(file).load()
File "/usr/lib/python2.7/pickle.py", line 858, in load
dispatch[key](self)
File "/usr/lib/python2.7/pickle.py", line 1083, in load_newobj
obj = cls.__new__(cls, *args)
AttributeError: class Reference has no attribute '__new__'
在 2013年3月29日星期五UTC+9上午5时42分42秒，Alex Burgel写道：
>
> Hi,
>
> I've been pickling some data to store in a datastore blob, and recently I
> tried to download and unpickle the data on my local machine. I got errors
> whenever I tried to do this because it seems like production uses a
> different version of ProtocolBuffers than the SDK.
>
> Part of the pickled data contained an appengine Key, which contains a
> reference to a google.appengine.datastore.entity_pb.Reference, which is a
> subclass of google.net.proto.ProtocolBuffer.ProtocolMessage. On the SDK,
> this is old-style python class. But it looks like its a new-style class on
> production. (Of course, I can't see the code, but it hasattr '__new__' and
> '__class__').
>
> I'm not sure if this is a bug. It seems like you should be able to pickle
> app engine classes, and it would be nice if you could read that data in the
> SDK.
>
> This is the exception that I get when trying to unpickle in the dev SDK:
>
> Traceback (most recent call last):
> File "<console>", line 1, in <module>
> File
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.py",
>
> line 1382, in loads
> return Unpickler(file).load()
> File
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.py",
>
> line 858, in load
> dispatch[key](self)
> File
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.py",
>
> line 1083, in load_newobj
> obj = cls.__new__(cls, *args)
> AttributeError: class Reference has no attribute '__new__'
>
> --Alex
>
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