colour.hints.Union = typing.Union[source]#

Union type; Union[X, Y] means either X or Y.

On Python 3.10 and higher, the | operator can also be used to denote unions; X | Y means the same thing to the type checker as Union[X, Y].

To define a union, use e.g. Union[int, str]. Details: - The arguments must be types and there must be at least one. - None as an argument is a special case and is replaced by


  • Unions of unions are flattened, e.g.:

    assert Union[Union[int, str], float] == Union[int, str, float]
  • Unions of a single argument vanish, e.g.:

    assert Union[int] == int  # The constructor actually returns int
  • Redundant arguments are skipped, e.g.:

    assert Union[int, str, int] == Union[int, str]
  • When comparing unions, the argument order is ignored, e.g.:

    assert Union[int, str] == Union[str, int]
  • You cannot subclass or instantiate a union.

  • You can use Optional[X] as a shorthand for Union[X, None].