RFC: simplify/clarify inheritance hierarchy for yt.data_objects.unions.Union

yt/data_objects/particle_unions.py

@@ -1,8 +1,9 @@
-from .unions import Union
+from yt._maintenance.deprecation import issue_deprecation_warning
 
+from .unions import ParticleUnion  # noqa: F401
 
-class ParticleUnion(Union):
-    _union_type = "particle"
-
-    def __init__(self, name, sub_types):
-        super().__init__(name, sub_types)
+issue_deprecation_warning(
+    "Importing ParticleUnion from yt.data_objects.particle_unions is deprecated. "
+    "Please import this class from yt.data_objects.unions instead",
+    since="4.2",
+)

yt/data_objects/static_output.py

@@ -21,8 +21,8 @@
 from yt._maintenance.deprecation import issue_deprecation_warning
 from yt.config import ytcfg
 from yt.data_objects.particle_filters import filter_registry
-from yt.data_objects.particle_unions import ParticleUnion
 from yt.data_objects.region_expression import RegionExpression
+from yt.data_objects.unions import ParticleUnion
 from yt.fields.derived_field import ValidateSpatial
 from yt.fields.field_type_container import FieldTypeContainer
 from yt.fields.fluid_fields import setup_gradient_fields

yt/data_objects/unions.py

@@ -1,8 +1,13 @@
+from abc import ABC, abstractmethod
+
 from more_itertools import always_iterable
 
 
-class Union:
-    _union_type = ""
+class Union(ABC):
+    @property
+    @abstractmethod
+    def _union_type(self) -> str:
+        ...
 
     def __init__(self, name, sub_types):
         self.name = name
@@ -20,5 +25,6 @@ def __repr__(self):
 class MeshUnion(Union):
     _union_type = "mesh"
 
-    def __init__(self, name, sub_types):
-        super().__init__(name, sub_types)
+
+class ParticleUnion(Union):
+    _union_type = "particle"

yt/frontends/art/data_structures.py

@@ -8,8 +8,8 @@
 
 import yt.utilities.fortran_utils as fpu
 from yt.data_objects.index_subobjects.octree_subset import OctreeSubset
-from yt.data_objects.particle_unions import ParticleUnion
 from yt.data_objects.static_output import Dataset, ParticleFile
+from yt.data_objects.unions import ParticleUnion
 from yt.frontends.art.definitions import (
     amr_header_struct,
     constants,

yt/frontends/artio/data_structures.py

@@ -7,8 +7,8 @@
 
 from yt.data_objects.field_data import YTFieldData
 from yt.data_objects.index_subobjects.octree_subset import OctreeSubset
-from yt.data_objects.particle_unions import ParticleUnion
 from yt.data_objects.static_output import Dataset
+from yt.data_objects.unions import ParticleUnion
 from yt.frontends.artio import _artio_caller
 from yt.frontends.artio._artio_caller import (
     ARTIOSFCRangeHandler,

yt/frontends/stream/data_structures.py

@@ -19,9 +19,8 @@
     SemiStructuredMesh,
     UnstructuredMesh,
 )
-from yt.data_objects.particle_unions import ParticleUnion
 from yt.data_objects.static_output import Dataset, ParticleFile
-from yt.data_objects.unions import MeshUnion
+from yt.data_objects.unions import MeshUnion, ParticleUnion
 from yt.frontends.sph.data_structures import SPHParticleIndex
 from yt.funcs import setdefaultattr
 from yt.geometry.geometry_handler import Index, YTDataChunk

yt/frontends/ytdata/data_structures.py

@@ -8,13 +8,13 @@
 import numpy as np
 
 from yt.data_objects.index_subobjects.grid_patch import AMRGridPatch
-from yt.data_objects.particle_unions import ParticleUnion
 from yt.data_objects.profiles import (
     Profile1DFromDataset,
     Profile2DFromDataset,
     Profile3DFromDataset,
 )
 from yt.data_objects.static_output import Dataset, ParticleFile, validate_index_order
+from yt.data_objects.unions import ParticleUnion
 from yt.fields.field_exceptions import NeedsGridType
 from yt.fields.field_info_container import FieldInfoContainer
 from yt.funcs import is_root, parse_h5_attr