[C++-sig] Combining Boost Serialization with Boost Python

[Jim Bosch]

On 03/14/2012 04:37 PM, James Amundson wrote:
> I have a use case involving Boost Serialization and Boost Python. I have
> a (mostly) C++ library wrapped with Python. The C++ code uses Boost
> Serialization to periodically create checkpoints from which the user can
> resume later. Getting the serialization and python libraries to work
> together didn't present any special problems until I had a case in which
> the user had a derived Python class (from a C++ base). In searching the
> web, I have seen people asking about similar cases, but never an answer.
> See, e.g.,
> http://stackoverflow.com/questions/7289897/boost-serialization-and-boost-python-two-way-pickle
> <http://stackoverflow.com/questions/7289897/boost-serialization-and-boost-python-two-way-pickle>
> .
>

It's been a long while since I last tried to pickle Boost.Python 
objects, but I do recall being a lot happier with the level of control I 
had when I just implemented my own __reduce__ methods rather than 
relying on the __getstate__ and __setstate__ defined by 
enable_pickling().  In many cases, it was most convenient to actually 
just write __reduce__ in pure-Python and add it to the wrapped classes 
in the __init__.py file.  It would have to delegate to wrapped C++ 
methods to do the Boost.Serialization calls, of course.

Using __reduce__ would allow you to provide a specific callable to 
reconstruct the Python derived class, which could then ensure it does 
exactly the right combination of regular unpickling and C++ deserialization.

Sorry that's not the review of your "almost there" solution you were 
looking for, but I do think you might find the problem easier to solve 
with __reduce__.

Jim