DEPR: removed deprecated argument obj from GroupBy get_group

doc/source/whatsnew/v3.0.0.rst

@@ -96,6 +96,13 @@ Deprecations
 - Deprecated :meth:`Timestamp.utcnow`, use ``Timestamp.now("UTC")`` instead (:issue:`56680`)
 -
 
+.. ---------------------------------------------------------------------------
+.. _whatsnew_300.prior_deprecations:
+
+Removal of prior version deprecations/changes
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+- Removed deprecated argument ``obj`` in :meth:`.DataFrameGroupBy.get_group` and :meth:`.SeriesGroupBy.get_group` (:issue:`53545`)
+
 .. ---------------------------------------------------------------------------
 .. _whatsnew_300.performance:
 

pandas/core/groupby/groupby.py

@@ -1049,27 +1049,18 @@ def pipe(
         return com.pipe(self, func, *args, **kwargs)
 
     @final
-    def get_group(self, name, obj=None) -> DataFrame | Series:
+    def get_group(self, name) -> DataFrame | Series:
         """
         Construct DataFrame from group with provided name.
 
         Parameters
         ----------
         name : object
             The name of the group to get as a DataFrame.
-        obj : DataFrame, default None
-            The DataFrame to take the DataFrame out of.  If
-            it is None, the object groupby was called on will
-            be used.
-
-            .. deprecated:: 2.1.0
-                The obj is deprecated and will be removed in a future version.
-                Do ``df.iloc[gb.indices.get(name)]``
-                instead of ``gb.get_group(name, obj=df)``.
 
         Returns
         -------
-        same type as obj
+        DataFrame or Series
 
         Examples
         --------
@@ -1142,18 +1133,8 @@ def get_group(self, name, obj=None) -> DataFrame | Series:
         if not len(inds):
             raise KeyError(name)
 
-        if obj is None:
-            indexer = inds if self.axis == 0 else (slice(None), inds)
-            return self._selected_obj.iloc[indexer]
-        else:
-            warnings.warn(
-                "obj is deprecated and will be removed in a future version. "
-                "Do ``df.iloc[gb.indices.get(name)]`` "
-                "instead of ``gb.get_group(name, obj=df)``.",
-                FutureWarning,
-                stacklevel=find_stack_level(),
-            )
-            return obj._take_with_is_copy(inds, axis=self.axis)
+        indexer = inds if self.axis == 0 else (slice(None), inds)
+        return self._selected_obj.iloc[indexer]
 
     @final
     def __iter__(self) -> Iterator[tuple[Hashable, NDFrameT]]:

pandas/tests/groupby/test_groupby.py

@@ -526,16 +526,6 @@ def test_as_index_select_column():
     tm.assert_series_equal(result, expected)
 
 
-def test_obj_arg_get_group_deprecated():
-    depr_msg = "obj is deprecated"
-
-    df = DataFrame({"a": [1, 1, 2], "b": [3, 4, 5]})
-    expected = df.iloc[df.groupby("b").indices.get(4)]
-    with tm.assert_produces_warning(FutureWarning, match=depr_msg):
-        result = df.groupby("b").get_group(4, obj=df)
-        tm.assert_frame_equal(result, expected)
-
-
 def test_groupby_as_index_select_column_sum_empty_df():
     # GH 35246
     df = DataFrame(columns=Index(["A", "B", "C"], name="alpha"))