Add SDMX input/output

.pre-commit-config.yaml

@@ -5,6 +5,7 @@ repos:
   - id: mypy
     additional_dependencies:
     - importlib_resources
+    - lxml-stubs
     - nbclient
     - pint
     - pytest

doc/compat-sdmx.rst

@@ -1,24 +1,35 @@
+.. currentmodule:: genno.compat.sdmx
+
 SDMX (:mod:`.compat.sdmx`)
 **************************
 
 :doc:`Package documentation <sdmx1:index>`
 
+.. automodule:: genno.compat.sdmx
+
 Note that this package is available in PyPI as ``sdmx1``.
 To install the correct package, use:
 
 .. code-block:: sh
 
    pip install genno[sdmx]
 
-To ensure the function is available:
+To ensure the operators are available:
 
 .. code-block:: python
 
    c = Computer()
-   c.require_compat("genno.compat.sdmx")
+   c.require_compat("sdmx")
    c.add(..., "codelist_to_groups", ...)
 
-.. currentmodule:: genno.compat.sdmx
-
-.. automodule:: genno.compat.sdmx
+.. automodule:: genno.compat.sdmx.operator
    :members:
+
+   .. autosummary::
+
+      codelist_to_groups
+      dataset_to_quantity
+      quantity_to_dataset
+      quantity_to_message
+
+   This module also registers an implementation of :func:`.write_report` that handles :class:`sdmx.message.DataMessage` objects, such as those produced by :func:`.quantity_to_message`.

doc/whatsnew.rst

@@ -1,8 +1,10 @@
 What's new
 **********
 
-.. Next release
-.. ============
+Next release
+============
+
+- New operators in :doc:`compat-sdmx`: :func:`.dataset_to_quantity`, :func:`.quantity_to_dataset`, :func:`.quantity_to_message` (:issue:`21`, :pull:`115`).
 
 v1.22.0 (2023-12-13)
 ====================

genno/compat/sdmx/__init__.py

@@ -0,0 +1,20 @@
+__all__ = [
+    "codelist_to_groups",
+]
+
+
+def __getattr__(name: str):
+    if name == "codelist_to_groups":
+        from warnings import warn
+
+        warn(
+            f"Import {name} from genno.compat.sdmx; use genno.compat.sdmx.operator or "
+            'Computer.require_compat("sdmx") instead',
+            FutureWarning,
+        )
+
+        from . import operator
+
+        return operator.codelist_to_groups
+    else:
+        raise AttributeError

genno/compat/sdmx/operator.py

@@ -0,0 +1,214 @@
+from typing import Dict, Hashable, Iterable, List, Mapping, Optional, Tuple, Union
+
+import genno
+from genno import Quantity
+
+try:
+    import sdmx
+except ModuleNotFoundError:  # pragma: no cover
+    HAS_SDMX = False
+else:
+    HAS_SDMX = True
+
+from . import util
+
+__all__ = [
+    "codelist_to_groups",
+    "dataset_to_quantity",
+    "quantity_to_dataset",
+    "quantity_to_message",
+]
+
+
+def codelist_to_groups(
+    codes: Union["sdmx.model.common.Codelist", Iterable["sdmx.model.common.Code"]],
+    dim: Optional[str] = None,
+) -> Mapping[str, Mapping[str, List[str]]]:
+    """Convert `codes` into a mapping from parent items to their children.
+
+    The returned value is suitable for use with :func:`~.operator.aggregate`.
+
+    Parameters
+    ----------
+    codes
+        Either a :class:`sdmx.Codelist <sdmx.model.common.Codelist>` object or any
+        iterable of :class:`sdmx.Code <sdmx.model.common.Code>`.
+    dim : str, optional
+        Dimension to aggregate. If `codes` is a code list and `dim` is not given, the
+        ID of the code list is used; otherwise `dim` must be supplied.
+    """
+    from sdmx.model.common import Codelist
+
+    if isinstance(codes, Codelist):
+        items: Iterable["sdmx.model.common.Code"] = codes.items.values()
+        dim = dim or codes.id
+    else:
+        items = codes
+
+    if dim is None:
+        raise ValueError("Must provide a dimension ID for aggregation")
+
+    groups = dict()
+    for code in filter(lambda c: len(c.child), items):
+        groups[code.id] = list(map(str, code.child))
+
+    return {dim: groups}
+
+
+def dataset_to_quantity(ds: "sdmx.model.common.BaseDataSet") -> Quantity:
+    """Convert :class:`DataSet <sdmx.model.common.BaseDataSet>` to :class:`.Quantity`.
+
+    Returns
+    -------
+    .Quantity
+        The quantity may have the attributes:
+
+        - "dataflow_urn": :attr:`urn <sdmx.model.common.IdentifiableArtefact.urn>` of
+          the :class:`Dataflow <sdmx.model.common.BaseDataflow` referenced by the
+          :attr:`described_by <sdmx.model.common.BaseDataSet.described_by>` attribute of
+          `ds`, if any.
+        - "structure_urn": :attr:`urn <sdmx.model.common.IdentifiableArtefact.urn>` of
+          the :class:`DataStructureDefinition
+          <sdmx.model.common.BaseDataStructureDefinition>` referenced by the
+          :attr:`structured_by <sdmx.model.common.BaseDataSet.structured_by>` attribute
+          of `ds`, if any.
+    """
+    # Assemble attributes
+    attrs: Dict[str, str] = {}
+    if ds.described_by:  # pragma: no cover
+        attrs.update(dataflow_urn=util.urn(ds.described_by))
+    if ds.structured_by:
+        attrs.update(structure_urn=util.urn(ds.structured_by))
+
+    return Quantity(sdmx.to_pandas(ds), attrs=attrs)
+
+
+def quantity_to_dataset(
+    qty: Quantity,
+    structure: "sdmx.model.common.BaseDataStructureDefinition",
+    *,
+    observation_dimension: Optional[str] = None,
+    version: Union["sdmx.format.Version", str, None] = None,
+) -> "sdmx.model.common.BaseDataSet":
+    """Convert :class:`.Quantity` to :class:`DataSet <sdmx.model.common.BaseDataSet>`.
+
+    The resulting data set is structure-specific.
+
+    Parameters
+    ----------
+    observation_dimension : str or sdmx.model.common.DimensionComponent, optional
+        If given, the resulting data set is arranged in series, with the
+        `observation_dimension` varying across observations within each series. If not
+        given, the data set is flat, with all dimensions specified for each observation.
+    version : str or sdmx.format.Version, optional
+        SDMX data model version to use; default 2.1.
+    """
+    # Handle `version` argument, identify classes
+    _, DataSet, Observation = util.handle_version(version)
+    Key = sdmx.model.common.Key
+    SeriesKey = sdmx.model.common.SeriesKey
+
+    # Narrow type
+    # NB This is necessary because BaseDataStructureDefinition.measures is not defined
+    # TODO Remove once addressed upstream
+    assert isinstance(
+        structure,
+        (
+            sdmx.model.v21.DataStructureDefinition,
+            sdmx.model.v30.DataStructureDefinition,
+        ),
+    )
+
+    try:
+        # URN of DSD stored on `qty` matches `structure`
+        assert qty.attrs["structure_urn"] == util.urn(structure)
+    except KeyError:
+        pass  # No such attribute
+
+    # Dimensions; should be equivalent to the IDs of structure.dimensions
+    dims = qty.dims
+
+    # Create data set
+    ds = DataSet(structured_by=structure)
+    measure = structure.measures[0]
+
+    if od := util.handle_od(observation_dimension, structure):
+        # Index of `observation_dimension`
+        od_index = dims.index(od.id)
+        # Group data / construct SeriesKey all *except* the observation_dimension
+        series_dims = list(dims[:od_index] + dims[od_index + 1 :])
+        grouped: Iterable = qty.to_series().groupby(series_dims)
+        # For as_obs()
+        obs_dims: Tuple[Hashable, ...] = (od.id,)
+        key_slice = slice(od_index, od_index + 1)
+    else:
+        # Pseudo-groupby object
+        grouped = [(None, qty.to_series())]
+        obs_dims, key_slice = dims, slice(None)
+
+    def as_obs(key, value):
+        """Convert a single pd.Series element to an sdmx Observation."""
+        return Observation(
+            # Select some or all elements of the SeriesGroupBy key
+            dimension=structure.make_key(Key, dict(zip(obs_dims, key[key_slice]))),
+            value_for=measure,
+            value=value,
+        )
+
+    for series_key, data in grouped:
+        if series_key:
+            sk = structure.make_key(SeriesKey, dict(zip(series_dims, series_key)))
+        else:
+            sk = None
+
+        # - Convert each item to an sdmx Observation.
+        # - Add to `ds`, associating with sk
+        ds.add_obs([as_obs(key, value) for key, value in data.items()], series_key=sk)
+
+    return ds
+
+
+def quantity_to_message(
+    qty: Quantity, structure: "sdmx.model.v21.DataStructureDefinition", **kwargs
+) -> "sdmx.message.DataMessage":
+    """Convert :class:`.Quantity` to :class:`DataMessage <sdmx.message.DataMessage>`.
+
+    Parameters
+    ----------
+    kwargs :
+        `observation_dimension` and `version` parameters are both used and passed on
+        to :func:`.quantity_to_dataset`.
+    """
+    kwargs.update(
+        version=util.handle_version(kwargs.get("version"))[0],
+        observation_dimension=util.handle_od(
+            kwargs.get("observation_dimension"), structure
+        ),
+    )
+
+    ds = quantity_to_dataset(
+        qty,
+        structure,
+        observation_dimension=kwargs["observation_dimension"],
+        version=kwargs["version"],
+    )
+
+    return sdmx.message.DataMessage(data=[ds], **kwargs)
+
+
+@genno.operator.write_report.register
+def _(obj: "sdmx.message.DataMessage", path, kwargs=None) -> None:
+    """Write  `obj` to the file at `path`.
+
+    If `obj` is a :class:`sdmx.message.DataMessage` and `path` ends with ".xml", use
+    use :mod:`sdmx` methods to write the file to SDMX-ML. Otherwise, equivalent to
+    :func:`genno.operator.write_report`.
+    """
+    import genno.compat.sdmx.operator  # noqa: F401
+
+    assert path.suffix.lower() == ".xml"
+
+    kwargs = kwargs or {}
+    kwargs.setdefault("pretty_print", True)
+
+    path.write_bytes(sdmx.to_xml(obj, **kwargs))

genno/compat/sdmx/util.py

@@ -0,0 +1,54 @@
+from typing import Optional, Tuple, Type, Union
+
+import sdmx
+
+
+def handle_od(
+    value: Union[str, "sdmx.model.common.DimensionComponent", None],
+    structure: "sdmx.model.common.BaseDataStructureDefinition",
+) -> Optional["sdmx.model.common.DimensionComponent"]:
+    """Handle `observation_dimension` arguments for :mod:`.sdmx.operator`.
+
+    Ensure either None or a DimensionComponent.
+    """
+    import sdmx
+
+    if isinstance(value, sdmx.model.common.DimensionComponent) or value is None:
+        return value
+    elif value is not None:
+        return structure.dimensions.get(value)
+
+
+def urn(obj: "sdmx.model.common.MaintainableArtefact") -> str:
+    """Return the URN of `obj`, or construct it."""
+    if result := obj.urn:  # pragma: no cover
+        return result
+    else:
+        return sdmx.urn.make(obj)
+
+
+def handle_version(
+    version: Union["sdmx.format.Version", str, None],
+) -> Tuple[
+    "sdmx.format.Version",
+    Type["sdmx.model.common.BaseDataSet"],
+    Type["sdmx.model.common.BaseObservation"],
+]:
+    """Handle `version` arguments for :mod:`.sdmx.operator`.
+
+    Also return either :mod:`sdmx.model.v21` or :mod:`sdmx.model.v30`, as appropriate.
+    """
+    from sdmx.format import Version
+
+    # Ensure a Version enum member
+    if not isinstance(version, Version):
+        version = Version[version or "2.1"]
+
+    # Retrieve information model module
+    im = {Version["2.1"]: sdmx.model.v21, Version["3.0.0"]: sdmx.model.v30}[version]
+
+    return (
+        version,
+        im.get_class("StructureSpecificDataSet"),
+        im.get_class("Observation"),
+    )