[Python-Dev] Re: [ python-Bugs-416670 ] MatchObjects not deepcopy()able

[Tim Peters]

[Fredrik Lundh]
> which leads to a followup question: the current approach
> seems to be to hack the copy.py file for each and every
> type.  imo, that's rather unpythonic, and also introduces
> lots of unnecessary module dependencies.
>
> time to add a __clone__ slot?

Note that classes can supply custom cloners via defining __copy__ and
__deepcopy__ methods, without changing copy.py.

A __clone__ slot for *types* would need to address the shallow vs deep
question too, along with the other __getinitargs__, __getstate__,
__setstate__ gimmicks.  How many slots does that add up to?  I leave it to
the PEP author to count them <wink>.

The copy.py protocols kinda grew up with pickle.py's, and together still have
the flavor (to my tongue) of a prototype caught late in midstream.  That is,
it feels like they're not quite finished yet.

> or could someone who knows what he's doing here address
> this comment in copy.py:
>
>     # XXX need to support copy_reg here too...

copy_reg is one of the pickle.py facilities that copy.py "should use" too;
it's a registration database that tells pickle what to do about objects of
types pickle doesn't understand directly (so *could* also be directly
relevant to cloning objects of types copy.py doesn't understand directly --
depending).