pickling new-style extension types: examples?
squan at web.de
Sat Apr 5 08:44:20 CEST 2003
Maciej Kalisiak <mac at die.spammer.die.dgp.toronto.edu> wrote in message news:<slrnb8scn8.d6f.mac at mac.dgp.toronto.edu>...
> I've implemented a new extension type in C, and am now attempting to make it
> picklable, with little success. Can someone point out any online examples of
> doing this, or even post some code snippets? Ideally I would want to implement
> the pickling functionality in C, but will settle for a Python class wrapper
> around the extension type, if necessary. Either the __reduce__ protocol, or
> using the "copy_reg" module will do.
To pickle an extension type you need
- a mechanism to "serialize" it (convert to a string) and
- one to reconstruct it from a string.
Then you write a Python wrapper class where you implement the special
__getstate__() and __setstate()__ which are called by the pickle
class Wrapper( object ):
def __init__( self ): self.c_object = CExtensionType( whatever )
def __getstate__( self ):
# Replace extension type instance by string converted version
self.c_object_str = serialize( self.c_object )
def __setstate__( self, state ): # state is a dict
state[ c_object ] = CExtensionType( state.c_cobject_str ) #
Reconstruct from string
del state[ c_object ] # delete string representation
self.__dict__.update( state )
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