Re: Pickling problems with the relax data storage singleton. -- November 23, 2007 - 09:15

Edward d'Auvergne wrote:

> Hi,
>
> Sorry.  Unfortunately the message missed the mailing.  Would you be
> able to resend it?
>
> Thanks,
>
> Edward
>
>
> On Nov 22, 2007 10:58 AM, Gary Thompson <garyt@xxxxxxxxxxxxxxx> wrote:
>  
>
> > Edward d'Auvergne wrote:
> >
> >    
> >
> > > On Nov 22, 2007 9:54 AM, Gary Thompson <garyt@xxxxxxxxxxxxxxx> wrote:
> > >
> > >
> > >      
> > >
> > > > Edward d'Auvergne wrote:
> > > >
> > > >
> > > >
> > > >        
> > > >
> > > > > Chris and Gary,
> > > > >
> > > > > Remember a long way back we had discussions about the following concept:
> > > > >
> > > > > -----
> > > > > class Data(dict):
> > > > >  """The relax data storage object."""
> > > > >
> > > > > [snip]
> > > > >
> > > > > # Rebind the name Data with an instance to prevent accidental creation
> > > > > # of multiple instances of the Data class
> > > > > Data = Data()
> > > > > -----
> > > > >
> > > > >
> > > > >
> > > > >          
> > > [snip]
> > >
> > >
> > >
> > >      
> > >
> > > > Can you give some details of how it fails? Is there an exception or does
> > > > it just replace the Data sinleton instance with a class instance?
> > > > Anyway i will dig further later in the week
> > > >
> > > >
> > > >        
> > > This can be seen by running the unit tests.  Just edit the file
> > > data/__init__.py which contains the singleton and raname both
> > > instances of Data2 to Data.  Then the unit test will give the relevent
> > > message:
> > >
> > > ======================================================================
> > > ERROR: The pickling and saving of the relax data storage singleton.
> > > ----------------------------------------------------------------------
> > > Traceback (most recent call last):
> > > File "/nmr5/edau/relax/relax-1.3/test_suite/unit_tests/state_testing_base.py",
> > > line 100, in test_save
> > >   self.state.save_state(file='test')
> > > File "/nmr5/edau/relax/relax-1.3/prompt/state.py", line 178, in save
> > >   save_state(file=file, dir=dir, force=force, compress_type=compress_type)
> > > File "/nmr5/edau/relax/relax-1.3/generic_fns/state.py", line 77, in save_state
> > >   dump(relax_data_store, file, 1)
> > > PicklingError: Can't pickle <class 'data.Data'>: it's not the same
> > > object as data.Data
> > >
> > > ======================================================================
> > >
> > > This looks like a possible namespace issue.  Maybe???
> > >
> > >
> > >
> > >
> > >      
> > >
> > > > regards
> > > > gary
> > > >
> > > > Of course one of the points here is that this isn't the only way to
> > > > write a singleton ;-)
> > > >
> > > >
> > > >        
> > > Of course, but I think we should still go with the way we voted.  We
> > > just need to work out how to pickle this thing.
> > >
> > > Cheers,
> > >
> > > Edward
> > >
> > >
> > > --
> > > Edward d'Auvergne
> > > Website:  http://nmr-relax.com
> > > Profile:  https://gna.org/users/bugman
> > >
> > > .
> > >
> > >
> > >
> > >      
> > Hi Ed
> >
> > from looking at the error here I think the problem is that python
> > internally thinks that Data() is still the classes constructor and is
> > suprised to find that it is a different object...
> >
> > I think the answer is on the following page
> > http://docs.python.org/lib/pickle-inst.html you need to define
> > __getstate__ and __setstate__ but...
> >
> > Its Worse than that he's Dead Jim
> > ---------------------------------
> >
> > There is possibly more that you have to do here, we need to check what
> > happens if two state pickles are read in: do we get two different
> > singletons ! What happens if we read in a pickle after already creating
> > a Data object...
> >
> > we definitley need to write some tests for these cases
> >
> >
> > regards
> > gary
> >
> > --
> > -------------------------------------------------------------------
> > Dr Gary Thompson
> > Astbury Centre for Structural Molecular Biology,
> > University of Leeds, Astbury Building,
> > Leeds, LS2 9JT, West-Yorkshire, UK             Tel. +44-113-3433024
> > email: garyt@xxxxxxxxxxxxxxx                   Fax  +44-113-2331407
> > -------------------------------------------------------------------
> >
> >
> >
> >    
>
> .
>
>  


--
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Dr Gary Thompson
Astbury Centre for Structural Molecular Biology,
University of Leeds, Astbury Building,
Leeds, LS2 9JT, West-Yorkshire, UK             Tel. +44-113-3433024
email: garyt@xxxxxxxxxxxxxxx                   Fax  +44-113-2331407
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