Re: using yaml_constructors attribute of the Loader class

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Kirill Simonov ha scritto:
> 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.
> 

My concern is that the new API will not allow me to do what I'm doing now.

As an example, if add_constructor is written in C and will store the
dictionary in C code, so that registered constructors are no more
accessible from Python code.


By the way, is yaml_constructors in old versions?


Thanks  Manlio
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