Hydra: How to express None in config files?

Question

I have a very simple Python script:

import hydra
from omegaconf import DictConfig, OmegaConf


@hydra.main(version_base="1.3", config_path=".", config_name="config")
def main(cfg: DictConfig) -> None:
    if cfg.benchmarking.seed_number is None: 
        raise ValueError()

if __name__ == "__main__": 
    main()

And here the config file:

benchmarking: 
  seed_number: None

Unfortunately, the Python script does not raise an error. Instead, when I print the type of cfg.benchmarking.seed_number, it is str. How can I pass None instead?

What value is `cfg.benchmarking.seed_number` being set to? `"None"` or something else? Does hydra document how it's config (yaml?) file is parsed? — Brian61354270, Jun 27 '23 at 18:29
You should use the word 'null' instead of None in the configuration file — MauriRamone, Jun 27 '23 at 18:49

score 6 · Accepted Answer · answered Jun 27 '23 at 20:25

6

Try null:

benchmarking: 
  seed_number: null

answered Jun 27 '23 at 20:25

Omry Yadan

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score 2 · Answer 2 · answered Jun 27 '23 at 23:12

In YAML format, it represents None as a string ("None").

To pass None as the value instead, you can replace it with !!null

benchmarking:
seed_number: !!null

Using !!null in the YAML configuration, it explicitly represents a null value.

But as this configuration is loaded into the Python, cfg.benchmarking.seed_number will be None instead of a string.

Hydra: How to express None in config files?

2 Answers2