Unions

X | Y or typing.Union[X, Y] can be used to expand inputs to multiple types.

import dataclasses
import enum
from typing import Literal, Optional

import tyro


class Color(enum.Enum):
    RED = enum.auto()
    GREEN = enum.auto()
    BLUE = enum.auto()


@dataclasses.dataclass(frozen=True)
class Args:
    # Unions can be used to specify multiple allowable types.
    union_over_types: int | str = 0
    string_or_enum: Literal["red", "green"] | Color = "red"

    # Unions also work over more complex nested types.
    union_over_tuples: tuple[int, int] | tuple[str] = ("1",)

    # And can be nested in other types.
    tuple_of_string_or_enum: tuple[Literal["red", "green"] | Color, ...] = (
        "red",
        Color.RED,
    )

    # Optional[T] is equivalent to `T | None`.
    integer: Optional[Literal[0, 1, 2, 3]] = None


if __name__ == "__main__":
    args = tyro.cli(Args)
    print(args)

---

python 01_basics/07_unions.py --help

usage: 07_unions.py [-h] [OPTIONS]

╭─ options ──────────────────────────────────────────────────────────────────╮
│ -h, --help                                                                 │
│     show this help message and exit                                        │
│ --union-over-types INT|STR                                                 │
│     Unions can be used to specify multiple allowable types. (default: 0)   │
│ --string-or-enum {red,green,RED,GREEN,BLUE}                                │
│     Unions can be used to specify multiple allowable types. (default: red) │
│ --union-over-tuples {INT INT}|STR                                          │
│     Unions also work over more complex nested types. (default: 1)          │
│ --tuple-of-string-or-enum [{red,green,RED,GREEN,BLUE}                      │
│ [{red,green,RED,GREEN,BLUE} ...]]                                          │
│     And can be nested in other types. (default: red RED)                   │
│ --integer {None,0,1,2,3}                                                   │
│     Optional[T] is equivalent to `T | None`. (default: None)               │
╰────────────────────────────────────────────────────────────────────────────╯