Accessing key name of parent

[jzazo]

Hi! I would like to access the parent key name of an attribute, probably via a resolver, would that be possible?
For example:

cfg = OmegaConf.create({"john": {"height": 180, "weight": 75, "player": "${parent_name:}"}})
cfg.john.player == "john"  # True

The reason is that I would like to pass the name of a parent to its children, e.g., a named storage that takes the name of the task that uses that storage system. Thank you!

[Jasha10]

Hi @jzazo!
I hope you don't mind using undocumented/internal OmegaConf methods, because I don't think this can be achieved with OmegaConf's public API.

Custom resolvers can take a special _parent_ argument (this part is documented, just before the "Built in Resolvers" section). This, in combination with the undocumented _key() method, will be enough to do the job:

from omegaconf import OmegaConf

def parent_name_impl(_parent_) -> str:
    return _parent_._key()

OmegaConf.register_new_resolver("parent_name", parent_name_impl)

cfg = OmegaConf.create({"john": {"height": 180, "weight": 75, "player": "${parent_name:}"}})
assert cfg.john.player == "john"

The standard caveats for undocumented/internal methods apply...

[jzazo]

Thanks a lot, your suggestion works great. I was wondering (for my use case), if it would be possible to get arbitrary grandparent name? Something like, given a node using relative interpolation, grab its parent, then grab its key? Would that be possible?

[jzazo]

I was thinking quite a convoluted solution: compute the path between the _root_ and the _parent_ of a node using dynamic programming, then once you have the path, grab the _key() at any level you want. Can you think of a better solution?

[Jasha10]

Can you think of a better solution?

I can, but my solution depends on OmegaConf's internals. Whether this will work for you depends on if you are willing to tie your project to OmegaConf's implementation details (which might change in the future!)

def grandparent_name_impl(_parent_) -> str:
    return _parent_._get_parent()._key()

See also Node._get_full_key, which returns a string representation of the full path from _root_ to the given node.

In the future I'll be working to extend OmegaConf's Unions feature to support unions of non-primitive types (e.g. types hints like Union[Dict[...], List[...]]. Once this is implemented, and if you use the unions feature, it's possible you'll find that Node._key() returns None for some container nodes (specifically if the node is wrapped inside a UnionNode).

[jzazo]

Thanks again, these proposals work and are cleaner. I think I would not use them with the Unions that you mention, but I will keep an eye for errors if I get Nones.