Re: [pyxser-users] problem serializing built-in and other types

[Daniel M. W. <dm...@co...>]

On Sunday 22 August 2010,
Vardan Akopian <vak...@gm...> wrote:

> Hi Daniel,
> 
> It looks like pyxser has a problem serializing built-in types when
> they are at the top level. For example each of the following will
> throw a "ValueError: Argument given for serialization/deserialization
> is not a Python Object or is None.":
> 
> pyxser.serialize(obj = 1, enc = 'utf-8')
> pyxser.serialize(obj = 'foo', enc = 'utf-8')
> pyxser.serialize(obj = ['foo'], enc = 'utf-8')
> pyxser.serialize(obj = ('foo'), enc = 'utf-8')
> pyxser.serialize(obj = {1:'foo'}, enc = 'utf-8')

  pyxser, pyxser XML schema and pyxser XML DTD are designed to serialize
objects with a constructor. Since those types of objects do not have
an accesible constructor from the C/API, I can't deserialize those objects
and pyxser can't deserialize those kinds of objects.

> 
> Also, an empty class also has the same problem:
> class Test: pass
> pyxser.serialize(obj = Test(), enc = 'utf-8')

  The same happens here. Those objects require a defined constructor
accesible from the Python C/API. The Python C/API just provides me
of PyInstance_NewRaw() for objects with argumented constructors and 
PyObject_CallFunctionObjArgs() for object with non-argumented
constructor. If you read the documentation you will notice that is
not possible to restore those instances.

> 
> But if I do
> x = Test()
> x.foo = 'foo'
> pyxser.serialize(obj = x, enc = 'utf-8')
> 
> then it works fine.
> 
> Is this by design, or am I using it wrongly?
> I encountered this when I was trying to serialize the result of
> User.all() that gets all the users through sqlalchemy.

  Yep, that works. If you want to serialize a list, like the 
User.all() is returning, I suggest that you must use a dummy
object:

x = Test()
x.foo = User.all()
pyxser.serialize(obj = x, enc = 'utf-8')

  This will work :)

> 
> Thanks.
> -Vardan

Best regards,
-- 
Daniel Molina Wegener <dmw [at] coder [dot] cl>
System Programmer & Web Developer
Phone: +56 (2) 979-0277 | Blog: http://coder.cl/