skunkwerk <skunkw...@gmail.com> writes: > Hi, > I'm using a custom pickler that replaces any un-pickleable objects (such as > sockets or files) with a string representation of them, based on the code > from Shane Hathaway here: > http://stackoverflow.com/questions/4080688/python-pickling-a-dict-with-some-unpicklable-items > > It works most of the time, but when I try to unpickle a Django HttpResponse, > I get the following error: > UnpicklingError: NEWOBJ class argument isn't a type object > > I have no clue what the error actually means.
The pickling protocol uses a form of bytecode which is executed during the unpickling to reconstruct the python objects based on their state found in the pickle alongside the bytecode. "NEWOBJ" is executed in response to such a bytecode operation. It expects to get a type as a parameter but in your case, it gets something else. > If it pickles okay, why should it not be able to unpickle? Any ideas? It is by principle impossible for the pickler to garantee that an unpickler will later succeed: the pickler does not know which classes/types are available for the unpickler. In your special case, the pickler could probably detect that unpickling will fail - but when an aim cannot be achieved completely this may provide motivation to abandon it as a whole - and not put much effort into a partial achievement. I have seen many cases where pickling succeeded but unpickling failed and in principle the pickler could have already predicted the failure (under the assumption that the unpickler sees the same classes/types as the pickler). If it is important for you to get Django HttpResponses successfully unpickled then you likely need to guide their pickling process better. Maybe (as an alternative), you can extract the relevant information from the "HttpResponse" and pickle that instead of the response itself? -- http://mail.python.org/mailman/listinfo/python-list
