Extend dataset_to_point_dict to accept both dataset and dict of dat…

…aarray (#7097)

pymc/util.py

@@ -239,18 +239,18 @@ def enhanced(*args, **kwargs):
 
 
 def dataset_to_point_list(
-    ds: xarray.Dataset, sample_dims: Sequence[str]
+    ds: Union[xarray.Dataset, dict[str, xarray.DataArray]], sample_dims: Sequence[str]
 ) -> Tuple[List[Dict[str, np.ndarray]], Dict[str, Any]]:
     # All keys of the dataset must be a str
-    var_names = list(ds.keys())
+    var_names = cast(List[str], list(ds.keys()))
     for vn in var_names:
         if not isinstance(vn, str):
             raise ValueError(f"Variable names must be str, but dataset key {vn} is a {type(vn)}.")
     num_sample_dims = len(sample_dims)
-    stacked_dims = {dim_name: ds[dim_name] for dim_name in sample_dims}
-    ds = ds.transpose(*sample_dims, ...)
+    stacked_dims = {dim_name: ds[var_names[0]][dim_name] for dim_name in sample_dims}
     stacked_dict = {
-        vn: da.values.reshape((-1, *da.shape[num_sample_dims:])) for vn, da in ds.items()
+        vn: da.transpose(*sample_dims, ...).values.reshape((-1, *da.shape[num_sample_dims:]))
+        for vn, da in ds.items()
     }
     points = [
         {vn: stacked_dict[vn][i, ...] for vn in var_names}

tests/test_util.py

@@ -156,16 +156,23 @@ def fn(a=UNSET):
     assert "a=UNSET" in captured.out
 
 
-def test_dataset_to_point_list():
-    ds = xarray.Dataset()
+@pytest.mark.parametrize("input_type", ("dict", "Dataset"))
+def test_dataset_to_point_list(input_type):
+    if input_type == "dict":
+        ds = {}
+    elif input_type == "Dataset":
+        ds = xarray.Dataset()
     ds["A"] = xarray.DataArray([[1, 2, 3]] * 2, dims=("chain", "draw"))
     pl, _ = dataset_to_point_list(ds, sample_dims=["chain", "draw"])
     assert isinstance(pl, list)
     assert len(pl) == 6
     assert isinstance(pl[0], dict)
     assert isinstance(pl[0]["A"], np.ndarray)
 
+
+def test_dataset_to_point_list_str_key():
     # Check that non-str keys are caught
+    ds = xarray.Dataset()
     ds[3] = xarray.DataArray([1, 2, 3])
     with pytest.raises(ValueError, match="must be str"):
         dataset_to_point_list(ds, sample_dims=["chain", "draw"])