OmegaConf: convert dict into List of Objects

Question

I am trying to automatically convert

from omegaconf import OmegaConf
s = """
nodes:
  node1:
   group: standard
   status: online
  node2:
   group: small
   status: online
  node3:
   group: standard
   status: offline
"""

into a list of nodes, where "node1/2/3" is the name of the node:

from dataclasses import dataclass
from typing import List

@dataclass
class Node:
  name: str
  group: str
  status: str

@dataclass
class Config:
  nodes: List[Node]

with

conf = OmegaConf.create(s)
schema = OmegaConf.structured(Config)
merged_conf = OmegaConf.merge(schema, conf)

Is there a mechanism in place for this? If I try it out-of-the-box I get

omegaconf.errors.ConfigTypeError: Cannot merge DictConfig with ListConfig

Answer 1

The error is telling you that you are attempting to merge a dictionary with a List, which is not supported. Your schema says that nodes is a List[Node], but your YAML string contains a mapping (YAML terminology for a dictionary).

Either change your schema to indicate that nodes is a Dict:

@dataclass
class Config:
  nodes: Dict[str, Node]

Or change your YAML string to contain a list:

s = """
nodes:
 - group: standard
   status: online
 - group: small
   status: online
 - group: standard
   status: offline
"""