[Python-Dev] Pickling failure on Enums (original) (raw)

Ethan Furman ethan at stoneleaf.us
Wed May 15 02:57:31 CEST 2013

On 05/14/2013 03:16 PM, Nick Coghlan wrote:

On 15 May 2013 07:38, "Guido van Rossum" <guido at python.org <mailto:guido at python.org>> wrote:

On Tue, May 14, 2013 at 2:13 PM, Ethan Furman <ethan at stoneleaf.us <mailto:ethan at stoneleaf.us>> wrote: > On 05/14/2013 01:58 PM, Guido van Rossum wrote: >> >> On Tue, May 14, 2013 at 1:09 PM, Ethan Furman <ethan at stoneleaf.us <mailto:ethan at stoneleaf.us>> wrote: >>> I can get pickle failure on members created using the functional syntax >>> with no module set; >> >> >> That's the case I care most about. > > > Good, 'cause that one is handled. :) Then we're good. >>> I cannot get pickle failure on those same classes; >> >> >> I suppose you mean "if you create the same enums using class syntax"? >> Sounds fine to me. > > > No. Example class: > > --> Example = Enum('Example', 'example ie eg') # no module name given, > frame hack fails > > --> pickle(Example.ie) > # blows up > > --# pickle(Example) > # succeeds here, but unpickle will fail Not great, but (a) few people pickle classes, and (b) there's probably something you can do to the metaclass to sabotage this. But it's fine to punt on this now. It may be a bug in pickle - it sounds like it is sanity checking type(obj), but not checking for cases where obj itself is a class.

Well, it's definitely not calling the metaclass' reduce as that's where I put the bomb (hmm, will I be visited by men in dark suits now?) so maybe that's a bug in pickle.

At any rate, I figured it out -- give the class' module a dummy name (I like 'uh uh' ;) and when pickle can't find that module it'll blow itself up.

-- Ethan

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