[Python-Dev] Extending types in C - help needed

[M.-A. Lemburg]

Jack Jansen wrote:
> 
> On Thursday, January 17, 2002, at 11:29  AM, M.-A. Lemburg wrote:
> 
> > I am more in favour of
> > exposing the pickle reduce API through "O@", that is
> > have PyArgTuple_Parse() call the .__reduce__() method
> > of the object. This will then return (factory, state_tuple)
> > and these could then be exposed to the C function via two
> > PyObject*.
> 
> You've suggested this before, but at that time I ignored it
> because it made absolutely no sense to me. "pickle" triggers one
> set of ideas for me, "reduce" triggers a different set, "factory
> function" yet another different set. None of these sets of ideas
> have the least resemblance to what I'm trying to do:-)

The idea is simple but extends what you are trying to
achieve (I gave an example on how to use this somewhere
in the "wrapper" thread). Basically, you'll just want to
use the state tuple to access the underlying void* C pointer
via a PyCObject which does the wrapping of the pointer.
The "pickle" mechanism would store the PyCObject in the
state tuple which you could then access to get at the
C pointer.
 
This may sound complicated at first, but it provides much
more flexibility w/r to more complex objects, e.g. the method
you have in mind only supports wrapping a single C pointer;
the "pickle" mechanism can potentially handle any serializable 
object.

> I gave a fairly complete example (using calldll from Python to
> wrap a function that returns a Mac WindowObject) last week,
> could you explain how you would implement this with pickle,
> reduce and factory functions?

Sorry, no time for that ... I've got an important business
trip next week which needs to be prepared. Please bring this
up again after next week.

-- 
Marc-Andre Lemburg
CEO eGenix.com Software GmbH
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