add open_virtual_dataarray

virtualizarr/__init__.py

@@ -1,6 +1,6 @@
 from virtualizarr.manifests import ChunkManifest, ManifestArray  # type: ignore # noqa
 from virtualizarr.accessor import VirtualiZarrDatasetAccessor  # type: ignore # noqa
-from virtualizarr.backend import open_virtual_dataset  # noqa: F401
+from virtualizarr.backend import open_virtual_dataset, open_virtual_dataarray  # noqa: F401
 
 from importlib.metadata import version as _version
 

virtualizarr/backend.py

@@ -7,7 +7,7 @@
     Optional,
 )
 
-from xarray import Dataset, Index
+from xarray import DataArray, Dataset, Index
 
 from virtualizarr.manifests import ManifestArray
 from virtualizarr.readers import (
@@ -198,3 +198,53 @@ def open_virtual_dataset(
     )
 
     return vds
+
+
+def open_virtual_dataarray(
+    filepath: str,
+    *,
+    filetype: FileType | None = None,
+    group: str | None = None,
+    drop_variables: Iterable[str] | None = None,
+    loadable_variables: Iterable[str] | None = None,
+    decode_times: bool | None = None,
+    indexes: Mapping[str, Index] | None = None,
+    virtual_array_class=ManifestArray,
+    reader_options: Optional[dict] = None,
+) -> DataArray:
+
+    drop_variables, loadable_variables = check_for_collisions(
+        drop_variables,
+        loadable_variables,
+    )
+
+    if virtual_array_class is not ManifestArray:
+        raise NotImplementedError()
+
+    if reader_options is None:
+        reader_options = {}
+
+    if filetype is not None:
+        # if filetype is user defined, convert to FileType
+        filetype = FileType(filetype)
+    else:
+        filetype = automatically_determine_filetype(
+            filepath=filepath, reader_options=reader_options
+        )
+
+    backend_cls = VIRTUAL_BACKENDS.get(filetype.name.lower())
+
+    if backend_cls is None:
+        raise NotImplementedError(f"Unsupported file type: {filetype.name}")
+
+    vda = backend_cls.open_virtual_dataarray(
+        filepath,
+        group=group,
+        drop_variables=drop_variables,
+        loadable_variables=loadable_variables,
+        decode_times=decode_times,
+        indexes=indexes,
+        reader_options=reader_options,
+    )
+
+    return vda

virtualizarr/readers/common.py

@@ -12,6 +12,7 @@
 
 from xarray import (
     Coordinates,
+    DataArray,
     Dataset,
     DataTree,
     Index,
@@ -93,11 +94,11 @@ def open_loadable_vars_and_indexes(
 
 
 def construct_virtual_dataset(
-    virtual_vars,
-    loadable_vars,
-    indexes,
-    coord_names,
-    attrs,
+    virtual_vars: Mapping[str, Variable],
+    loadable_vars: Mapping[str, Variable],
+    indexes: Mapping[str, Index],
+    coord_names: Iterable[str],
+    attrs: dict[str, str],
 ) -> Dataset:
     """Construct a virtual Datset from consistuent parts."""
 
@@ -117,6 +118,23 @@ def construct_virtual_dataset(
     return vds
 
 
+def construct_virtual_dataarray(
+    virtual_var: Variable,
+    loadable_vars: Mapping[str, Variable],
+    indexes: Mapping[str, Index],
+    coord_names: Iterable[str],
+    attrs: dict[str, str],
+) -> DataArray:
+
+    vda = DataArray(
+        data=virtual_var,
+        coords=coord_names,
+        # indexes={},  # TODO should be added in a later version of xarray
+        attrs=attrs,
+    )
+    return vda
+
+
 def separate_coords(
     vars: Mapping[str, Variable],
     indexes: MutableMapping[str, Index],
@@ -167,6 +185,18 @@ def separate_coords(
 
 
 class VirtualBackend(ABC):
+    @staticmethod
+    def open_virtual_dataarray(
+        filepath: str,
+        group: str | None = None,
+        drop_variables: Iterable[str] | None = None,
+        loadable_variables: Iterable[str] | None = None,
+        decode_times: bool | None = None,
+        indexes: Mapping[str, Index] | None = None,
+        reader_options: Optional[dict] = None,
+    ) -> DataArray:
+        raise NotImplementedError()
+
     @staticmethod
     def open_virtual_dataset(
         filepath: str,