OP_TREE= typing.Union[cirq.ops.raw_types.Operation, typing.Iterable[typing.Any]]¶
Union type; Union[X, Y] means either X or 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 type(None).
Unions of unions are flattened, e.g.:
Union[Union[int, str], float] == Union[int, str, float]
Unions of a single argument vanish, e.g.:
Union[int] == int # The constructor actually returns int
Redundant arguments are skipped, e.g.:
Union[int, str, int] == Union[int, str]
When comparing unions, the argument order is ignored, e.g.:
Union[int, str] == Union[str, int]
When two arguments have a subclass relationship, the least derived argument is kept, e.g.:
class Employee: pass class Manager(Employee): pass Union[int, Employee, Manager] == Union[int, Employee] Union[Manager, int, Employee] == Union[int, Employee] Union[Employee, Manager] == Employee
Similar for object:
Union[int, object] == object
You cannot subclass or instantiate a union.
You can use Optional[X] as a shorthand for Union[X, None].