[IronPython] Question about serialization

Curt Hagenlocher curt at hagenlocher.org
Wed Mar 26 17:37:42 CET 2008


I was thinking that Python's lack of a global namespace for classes would be
a problem -- but of course it's not because you'd actually be looking in the
CLR namespace.  So you could just fail the deserialize if the CLR base class
doesn't already exist.

It would still be nice to be able to auto-load an assembly when the base
class is strongly-named.

On Wed, Mar 26, 2008 at 8:42 AM, Dino Viehland <dinov at exchange.microsoft.com>
wrote:

>  My guess is you'd restrict it only to .NET objects which are marked as
> being serializable.  Then you'd ask the object to serialize it's self and
> then stuff that into the pickle stream along w/ the extra Python info.
> That's probably include a type name which you'd just load and see what you
> got – much like how cPickle does an import and uses what it gets when it's
> loading a global.
>
>
>
> *From:* users-bounces at lists.ironpython.com [mailto:
> users-bounces at lists.ironpython.com] *On Behalf Of *Curt Hagenlocher
> *Sent:* Wednesday, March 26, 2008 8:31 AM
> *To:* Discussion of IronPython
> *Subject:* Re: [IronPython] Question about serialization
>
>
>
> This is an interesting problem. Python's pickle writes out enough data to
> rebuild the object entirely -- including the class definition, if the object
> is a user-defined type.  How do you accurately write out a class definition
> for a C# base class?  Would you restrict it to strongly named classes?
>
>
>
>
> On Wed, Mar 26, 2008 at 4:55 AM, Paul Turbett <sls at iinet.net.au> wrote:
>
> Thanks Michael for the advice. Must appreciated. Unfortunately I hasn't
> worked out yet tho :(
>
> I can use pickle from C# using Evaluate, or from within a Python class, on
> a "pure" Python object. However any attempt at pickling a python object that
> derives from a C# base result in an exception like this:
> Cannot convert MyObject(<MyObject object at 0x000000000000002B>) to Int32
>
> Exploring further, I came across Ops.GetDynamicType() and
> Ops.GetAttrsNames() which I thought might be helpful to get the attributes
> of an object and serialize it somehow (manually), but GetAttrNames requires
> an ICallerContext, and I can't see how to get one of those.
>
> It seems that whilst serializing .NET classes is trivial, and serializing
> python classes is trivial, serializing something that touches both is
> proving quite difficult.
>
> Any further suggestions gratefully received!
>
> Thanks, Paul
>
> Michael Foord wrote:
>
> Paul Turbett wrote:
>
>
>
> Hi,
>
>
>
> I'm using IP as a scripting engine in a C# app. I have various Python
>
> classes that derive from a C# base class, and have there own additional
>
> data & functionality.
>
>
>
> I would like to be able to serialize instances of the Python classes
>
> from the C# host for persistence across sessions. Using the standard
>
> BinaryFormatter with the Serializable attribute is not working - I get
>
> an error about the python class not being marked as serializable (the C#
>
> base class is marked as serializable though).
>
>
>
> How can I serialize python objects from C#? Should I use reflection to
>
> roll my own serializer, or is there something in one of the lesser
>
> documented assemblies like Ops I should use?
>
>
>
>
>
> Typically for serializing Python objects you would use pickle [1]. The
>
> 'dumps' function returns a string (make sure you use the text protocol
>
> for IronPython).
>
>
>
> You could then execute code inside the Python engine to serialize /
>
> deserialize objects. I've not tried this for instances that inherit from
>
> C# base classes - but it should work fine. :-)
>
>
>
> Michael Foord
>
> http://www.ironpythoninaction.com
>
>
>
> .. [1] http://docs.python.org/lib/module-pickle.html
>
>
>
>
>
> I'm using IP 1.1.1 (but will move to 2.0 if that will help). Any
>
> pointers & advice greatly appreciated!
>
>
>
> Thanks, Paul
>
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