Using the config object

 

Here are some basic features of the Hydra Configuration Object:

config.yaml

node:                         # Config is hierarchical
  loompa: 10                  # Simple value
  zippity: ${node.loompa}     # Value interpolation
  do: "oompa ${node.loompa}"  # String interpolation
  waldo: ???                  # Missing value, must be populated prior to access

main.py

from omegaconf import DictConfig, OmegaConf
import hydra

@hydra.main(version_base=None, config_path=".", config_name="config")
def my_app(cfg: DictConfig):
    assert cfg.node.loompa == 10          # attribute style access
    assert cfg["node"]["loompa"] == 10    # dictionary style access

    assert cfg.node.zippity == 10         # Value interpolation
    assert isinstance(cfg.node.zippity, int)  # Value interpolation type
    assert cfg.node.do == "oompa 10"      # string interpolation

    cfg.node.waldo                        # raises an exception

if __name__ == "__main__":
    my_app()

Outputs:

$ python my_app.py 
Traceback (most recent call last):
  File "my_app.py", line 32, in my_app
    cfg.node.waldo
omegaconf.errors.MissingMandatoryValue: Missing mandatory value: node.waldo
    full_key: node.waldo
    object_type=dict

Hydra's configuration object is an instance of OmegaConf's DictConfig. You can learn more about OmegaConf here.