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DagsterNothingDataset

kedro_dagster.datasets.nothing_dataset.DagsterNothingDataset

Bases: AbstractDataset

A Kedro dataset used to represent placeholder outputs.

This dataset can be used in Kedro pipelines to signify that a node has completed its task without actually producing any tangible output. It is particularly useful for enforcing execution order in pipelines where certain nodes need to run after others without passing data.

Parameters

Name Type Description Default
metadata dict[str, Any] or None

Optional metadata stored alongside the dataset.

 None

Examples

>>> from kedro_dagster.datasets.nothing_dataset import DagsterNothingDataset
>>> nothing_ds = DagsterNothingDataset(metadata={"info": "no output"})
>>> data = nothing_ds.load()
>>> print(data)
__nothing__
>>> nothing_ds.save(data)

See Also

kedro_dagster.utils.is_nothing_asset_name : Predicate that checks whether a catalog entry is this type.

Source Code

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class DagsterNothingDataset(AbstractDataset):
    """A Kedro dataset used to represent placeholder outputs.

    This dataset can be used in Kedro pipelines to signify that a node has
    completed its task without actually producing any tangible output. It is
    particularly useful for enforcing execution order in pipelines where
    certain nodes need to run after others without passing data.

    Parameters
    ----------
    metadata : dict[str, Any] or None, optional
        Optional metadata stored alongside the dataset.

    Examples
    --------
    >>> from kedro_dagster.datasets.nothing_dataset import DagsterNothingDataset
    >>> nothing_ds = DagsterNothingDataset(metadata={"info": "no output"})
    >>> data = nothing_ds.load()
    >>> print(data)
    __nothing__
    >>> nothing_ds.save(data)

    See Also
    --------
    `kedro_dagster.utils.is_nothing_asset_name` :
        Predicate that checks whether a catalog entry is this type.
    """

    def __init__(
        self,
        metadata: dict[str, Any] | None = None,
    ) -> None:
        super().__init__()

        self._metadata = metadata or {}

    def load(self) -> str:
        """Return the nothing sentinel for every load.

        Returns
        -------
        str
            Always ``"__nothing__"``.
        """
        return NOTHING_OUTPUT

    def save(self, data: Any) -> None:
        """Do nothing when saving data.

        Parameters
        ----------
        data : Any
            Ignored.
        """
        # Intentionally do not persist anything
        pass

    def _exists(self) -> bool:
        """Always report that the dataset exists.

        Returns
        -------
        bool
            Always ``True``.
        """
        return True

    def _describe(self) -> dict[str, Any]:
        """Return a JSON-serializable description of the dataset.

        Returns
        -------
        dict[str, Any]
            Basic dataset type info.
        """
        return {"type": self.__class__.__name__}

Methods

load()

Return the nothing sentinel for every load.

Returns
Type Description
str

Always "__nothing__".
Source Code

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def load(self) -> str:
    """Return the nothing sentinel for every load.

    Returns
    -------
    str
        Always ``"__nothing__"``.
    """
    return NOTHING_OUTPUT

save(data)

Do nothing when saving data.

Parameters
Name Type Description Default
data Any

Ignored.

 required
Source Code

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def save(self, data: Any) -> None:
    """Do nothing when saving data.

    Parameters
    ----------
    data : Any
        Ignored.
    """
    # Intentionally do not persist anything
    pass