On Sunday 18 July 2010 11:16:29 John Reid wrote: > I'm not sure what you mean by mix-in, but my first attempt involved > defining pickle suite getstate() and setstate() methods. I did not > define a getinitargs() method. Unfortunately when the derived object was > unpickled, __init__ was called with no arguments. As far as I can see > there's no way to use the boost.python pickle suite that does not > involve a call to __init__() on the unpickled object.
How should it work? A proper object of a BPL extension type needs a wrapped C++ object "behind it". Thus, if you unpickle such an object, the corresponding C++ object needs to be created. There's the difference between pure python and BPL classes: with pure Python, you (or the pickle module) may just assign __class__, restore all attributes and be done. For C++ objects OTOH, pickle cannot list or restore the attributes, or make sure that the object is in any defined state. So you *need* to call a constructor, which may need arguments, hence the getinitargs(). In the __reduce__ hack within your last mail, you explicitly call __init__ with a single self arg, relying on a default constructible class, and relying on the fact that the C++ object will be in the same state as before. (That's probably fine, since you originally wrote that you're dealing with interfaces w/o state, but I wanted to point it out again for the unwary readers.) Have a nice day, Hans _______________________________________________ Cplusplus-sig mailing list Cplusplus-sig@python.org http://mail.python.org/mailman/listinfo/cplusplus-sig
