Serializing functions

[Matteo Landi]

On Thu, 2010-06-17 at 08:31 -0700, Stephen Hansen wrote:
> On 6/17/10 6:23 AM, Matteo Landi wrote:
> > itself. If you try and pickle a function, it is not pickled as a whole,
> > indeed, once you unpickle it, it will raise an exception telling you
> > that the target function was not found in the current module.
> 
> You can pickle functions-- and classes, instances, and such-- just fine.
> If you're having specific difficulty with one instance of doing so, show
> the actual code.
> 
> >>> def test(one):
> ...     print one + 1
> ...
> >>> import pickle
> >>> outp = pickle.dumps(test)
> >>> outp
> 'c__main__\ntest\np0\n.'
> >>> fn = pickle.loads(outp)
> >>> fn(1)
> 2
> 
> Now, complex stuff like classes and functions have to "live" in the same
> place with pickle, and it does need the source to be available and
> already imported, but it works fine.
> 
> If by "pickle a function" you mean, "take an arbitrary function and
> pickle it into some random destination and have it by itself still be
> enough to be executable", then no, pickle doesn't do that. To get that,
> you'd have to distribute the source to the destination and import it
> before-hand.

This is the problem, and I excuse me if I ain't been clear enough while
showing it inside my previous email.

> 
> That or do some crazy-complicated sort of code object marshalling and
> manipulation on the other side. I have no idea where to even begin in
> that situation (hoooow do you turn a code object into something you can
> actually pass arguments to, hmm? I only know how to 'exec' a bare code
> object)
> 

So it seems one should go for sending the function and the module with
its definition in order to make the remote side able to execute it.

I'm curious to see how picloud is able to discover the needed modules,
sources etc etc to run the function specified inside picloud.call(); it
seems not an easy task.

-- 
Matteo Landi
http://www.matteolandi.net