Remove NDFrame.__constructor_expanddim

Author: topper-123

doc/source/development/extending.rst

@@ -329,21 +329,11 @@ Each data structure has several *constructor properties* for returning a new
 data structure as the result of an operation. By overriding these properties,
 you can retain subclasses through ``pandas`` data manipulations.
 
-There are 3 constructor properties to be defined:
+There are 3 possible constructor properties to be defined on a subclass:
 
-* ``_constructor``: Used when a manipulation result has the same dimensions as the original.
-* ``_constructor_sliced``: Used when a manipulation result has one lower dimension(s) as the original, such as ``DataFrame`` single columns slicing.
-* ``_constructor_expanddim``: Used when a manipulation result has one higher dimension as the original, such as ``Series.to_frame()``.
-
-Following table shows how ``pandas`` data structures define constructor properties by default.
-
-===========================  ======================= =============
-Property Attributes          ``Series``              ``DataFrame``
-===========================  ======================= =============
-``_constructor``             ``Series``              ``DataFrame``
-``_constructor_sliced``      ``NotImplementedError`` ``Series``
-``_constructor_expanddim``   ``DataFrame``           ``NotImplementedError``
-===========================  ======================= =============
+* ``DataFrame/Series._constructor``: Used when a manipulation result has the same (sub-)class as the original.
+* ``DataFrame._constructor_sliced``: Used when a ``DataFrame`` (sub-)class manipulation result should be a ``Series`` (sub-)class.
+* ``Series._constructor_expanddim``: Used when a ``Series`` (sub-)class manipulation result should be a ``DataFrame`` (sub-)class, e.g. ``Series.to_frame()``.
 
 Below example shows how to define ``SubclassedSeries`` and ``SubclassedDataFrame`` overriding constructor properties.
 

doc/source/whatsnew/v1.3.0.rst

@@ -174,7 +174,7 @@ See :ref:`install.dependencies` and :ref:`install.optional_dependencies` for mor
 Other API changes
 ^^^^^^^^^^^^^^^^^
 - Partially initialized :class:`CategoricalDtype` (i.e. those with ``categories=None`` objects will no longer compare as equal to fully initialized dtype objects.
--
+- Accessing ``_constructor_expanddim`` on a :class:`DataFrame` and ``_constructor_sliced`` on a :class:`Series` now raise an ``AttributeError``. Previously a ``NotImplementedError`` was raised (:issue:`38782`)
 -
 
 .. ---------------------------------------------------------------------------

pandas/core/frame.py

@@ -490,20 +490,12 @@ class DataFrame(NDFrame, OpsMixin):
     _HANDLED_TYPES = (Series, Index, ExtensionArray, np.ndarray)
     _accessors: Set[str] = {"sparse"}
     _hidden_attrs: FrozenSet[str] = NDFrame._hidden_attrs | frozenset([])
-    _constructor_sliced: Type[Series] = Series
 
     @property
     def _constructor(self) -> Type[DataFrame]:
         return DataFrame
 
-    @property
-    def _constructor_expanddim(self):
-        # GH#31549 raising NotImplementedError on a property causes trouble
-        #  for `inspect`
-        def constructor(*args, **kwargs):
-            raise NotImplementedError("Not supported for DataFrames!")
-
-        return constructor
+    _constructor_sliced: Type[Series] = Series
 
     # ----------------------------------------------------------------------
     # Constructors

pandas/core/generic.py

@@ -375,14 +375,6 @@ def _constructor(self: FrameOrSeries) -> Type[FrameOrSeries]:
         """
         raise AbstractMethodError(self)
 
-    @property
-    def _constructor_expanddim(self):
-        """
-        Used when a manipulation result has one higher dimension as the
-        original, such as Series.to_frame()
-        """
-        raise NotImplementedError
-
     # ----------------------------------------------------------------------
     # Internals
 

pandas/core/series.py

@@ -401,6 +401,10 @@ def _constructor(self) -> Type["Series"]:
 
     @property
     def _constructor_expanddim(self) -> Type["DataFrame"]:
+        """
+        Used when a manipulation result has one higher dimension as the
+        original, such as Series.to_frame()
+        """
         from pandas.core.frame import DataFrame
 
         return DataFrame

pandas/tests/frame/test_api.py

@@ -330,11 +330,13 @@ def test_set_flags(self, allows_duplicate_labels, frame_or_series):
         assert obj.iloc[key] == 0
 
     def test_constructor_expanddim_lookup(self):
-        # GH#33628 accessing _constructor_expanddim should not
-        #  raise NotImplementedError
+        # GH#33628 accessing _constructor_expanddim should not raise NotImplementedError
+        # GH38782 pandas has no container higher than DatafFame (two-dim), so
+        # DataFrame._constructor_expand_dim, doesn't make sense, so is removed.
         df = DataFrame()
 
-        with pytest.raises(NotImplementedError, match="Not supported for DataFrames!"):
+        msg = "'DataFrame' object has no attribute '_constructor_expanddim'"
+        with pytest.raises(AttributeError, match=msg):
             df._constructor_expanddim(np.arange(27).reshape(3, 3, 3))
 
     @skip_if_no("jinja2")