Re: [Yaml-core] PyYAML constructor with mixed attributes

[Kirill S. <xi...@ga...>]

Hi Fabrizio,

> Using the python object constructor capability of YAML, I am trying to
> saparate object attributes in those that are not configurable (set at
> init time by the application code) and in those that are configurable
> (loaded at init time by YAML). One possible solution is in the following
> example. I dont like it very much, there is any better way to do it?
> Thanks in advance for any help.

PyYAML uses the pickle protocol (see PEP 307) to construct YAMLObject 
instances and thus it never calls the __init__ constructor.  By default, 
PyYAML simply updates the __dict__ dictionary with the content of the 
YAML node.  You may override this behavior by providing a __setstate__ 
method accepting a single argument 'state', which is the node content.

For instance, if you add a __setstate__ method to your Test class, the 
object corresponding to the document:

--- !Test
yaml_attr: attribute from yaml

will be constructed in the following way:

obj = create a new Test object, but don't call Test.__init__()
obj.__setstate__({'yaml_attr': 'attribute from yaml'})
return obj

Thanks,
Kirill