Custom resolver to select a field from a DictConfig

Question

nodes:
  node1: 1
  node2: 2
  node3: 3

selected_node: ${subfield:${nodes},node1}

Can I make a subfield resolver that returns nodes["node1"] and stores it in selected_node?

My attempts so far result in this error:

omegaconf.errors.GrammarParseError: token recognition error at: '{'
    full_key: selected_node
    object_type=dict

Answer 1

from omegaconf import OmegaConf
s = """
nodes:
  node1: 1
  node2: 2
  node3: 3

selected: ${subfield:${nodes},node1}
"""

def _subfield(node, field):
    return node[field]


OmegaConf.register_new_resolver("subfield", _subfield)
a = OmegaConf.create(s)
print(a.selected) # -> 1