tyro

tyro generates command-line interfaces directly from type hints. iron-monk uses standard dataclasses without metaclass tricks, so the two compose cleanly: tyro parses sys.argv, iron-monk enforces the business rules.

Project: https://github.com/brentyi/tyro

import sys
import tyro
import pathlib
from typing import Annotated

from monk import monk, validate
from monk.constraints import NonNegative, OneOf, Len, IsDir
from monk.exceptions import ValidationError

@monk
class CLIArgs:
    target_dir: Annotated[pathlib.Path, IsDir]
    tags: list[Annotated[str, Len(min_len=3)]]
    max_warnings: Annotated[int, NonNegative] = 10
    output_format: Annotated[str, OneOf(["json", "text", "html"])] = "text"

def main() -> None:
    # tyro parses sys.argv and builds the dataclass
    args = tyro.cli(CLIArgs)

    # iron-monk validates the values
    try:
        valid_args = validate(args)
    except ValidationError as e:
        print("Invalid arguments:\n", file=sys.stderr)
        for err in e.errors:
            print(f"  --{err['field'].replace('_', '-')}: {err['message']}", file=sys.stderr)
        sys.exit(1)

    print(f"Linting target: {valid_args.target_dir}")

if __name__ == "__main__":
    main()

Output

$ python cli_tyro.py --target-dir not-a-path --max-warnings -1 --tags john kelly smith bo --output-format yml

Invalid arguments:

  --target-dir: Must be an existing directory.
  --tags[3]: Must have a minimum length of 3.
  --max-warnings: Must be greater than or equal to 0.
  --output-format: Must be one of: ['json', 'text', 'html'], got 'yml'.