Re: using yaml_constructors attribute of the Loader class

Manlio Perillo wrote:
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> 
> Hi.
> 
> In a framework I'm writing I have a custom YAML Loader, with several
> custom constructors.
> 
> Now, I would like to allow applications to define their own
> constructors, and have them be used by my framework.
> 
> Using setuptools entry points, the code is something like this:
> 
> 
> from pkg_resources import iter_entry_points
> from yaml.loader import Loader
> 
> class MyLoader(Loader):
>     def factory(cls)
>         yaml_constructors = cls.yaml_constructors
>         for ep in iter_entry_points('my.entrypoint'):
>             yl = ep.load()
> 
>             yaml_constructors.update(yl.yaml_constructors)
> 
>         d = dict(yaml_constructors=yaml_constructors)
>         return type('MyLoader', (cls,), d)
> 
> Applications just need to create a custom loader class, derived from
> yaml.loader.Loader, and register their own constructors.
> 
> Is it "safe" (that is, is the API stable) to access the
> yaml_constructors attribute of the Loader class?
> 

Well, `yaml_constructors` is not a part of the documented API, but I 
don't think it's going to be removed any time soon.  In the worst case, 
you could always add a check for yaml.__version__:

if yaml.__version__ < 'X.Y':
     # Use yaml_constructors here
else:
     # Use the brand new API here.


Thanks,
Kirill

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