FWIW I found that I was able to pickle C++ objects but simply adding python methods __reduce__ and __setstate__ in my SWIG .i file -- I'm not sure if Matplotlib uses this approach or not. I didn't need to use copy_reg (perhaps it's preferable? I don't know)
http://freesteam.cvs.sourceforge.net/freesteam/freesteam/freesteam.i?revision=1.16&view=markup (this is from the steam properties project that I run, http://freesteam.sf.net/) Cheers JP Bryan Cole wrote: >On Sun, 2006-06-18 at 00:05 +1000, John Pye wrote: > > >>Hi all, >> >>A thought just occurred to me: I wonder if it would be useful to be able >>to 'pickle' Matplotlib plots, using the python cPickle library. This >>way, I could save my plots in a form that would allow me to load them >>back later (with just the necessary source data) and fiddle with things >>like titles and legends and so on. Would be useful perhaps in the >>context of preparing diagrams for an article or report. >> >>Has anyone tried this? Would it be recommended/not recommended/not even >>possible? >> >> > >I had a look at this a while back. It looks like the well thought out >structure of MPL should make this easy, although it would require a few >adjustments. To make a Figure object pickle-able, all the internal >objects in a Figure must also be pickle-able. Most of the innards of a >Figure are python objects which should pickle without problem. The only >parts which aren't are the "BinOps". These are custom C-coded objects >which implement 'lazy evaluation' of the transformation expressions. >They're defined in the _transforms.cxx/h files. > >In theory, you can easily make these C-objects pickle-able using the >'copy_reg' module; you just register two functions, one to extracts the >object's state as a pickle-able object, the other to construct a new >instance of the object, initialised with the previously stored state. > >However, I ran into a problem: there's some bug in either python or CXX >(the automatic C++ class wrapper which mpl uses for the compiled >components) which results in a segfault when I tried pickling copy_reg >enhanced BinOps. The templating techniques used by CXX are completely >beyond me so this is where things have stuck. > >... but ... I just now tested this again with python-2.4.2 and >mpl-0.87.2 and it works! yeay. Thus, if every object in >matplotlib._transforms gets given a python reduction/construction >function pair and registers them with copy_reg, this *should* be enough >to make a Figure pickle-able. Unless I've missed something else... > >I may try this out later this week, unless someone else tries it first. > >Bryan > >PS. copy_reg example follows >>> > >import cPickle as pickle >import copy_reg > >#let's test this on a simple 'Value' BinOp >from matplotlib._transforms import Value > >def fcon(val): > #constructor > return Value(val) > >def fred(o): > #reduction functions > val = o.get() > return fcon, (val,) > >#my starting object >a=Value(5) >print a, a.get() > >copy_reg.pickle(type(a), fred) > >data = pickle.dumps(a) > >new = pickle.loads(data) >print "new", new, new.get() > > > >>Cheers >>JP >> >> > > > > >_______________________________________________ >Matplotlib-users mailing list >Matplotlib-users@lists.sourceforge.net >https://lists.sourceforge.net/lists/listinfo/matplotlib-users > > > _______________________________________________ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
