Initial version

Author: datapythonista

doc/source/whatsnew/v1.5.3.rst

@@ -33,6 +33,7 @@ Bug fixes
 - Bug when chaining several :meth:`.Styler.concat` calls, only the last styler was concatenated (:issue:`49207`)
 - Fixed bug when instantiating a :class:`DataFrame` subclass inheriting from ``typing.Generic`` that triggered a ``UserWarning`` on python 3.11 (:issue:`49649`)
 - Bug in :func:`pandas.testing.assert_series_equal` (and equivalent ``assert_`` functions) when having nested data and using numpy >= 1.25 (:issue:`50360`)
+- Bug in :meth:`DataFrame.loc` leading to unwanted `FutureWarning` (:issue:`48673`)
 -
 
 .. ---------------------------------------------------------------------------

pandas/core/indexing.py

@@ -2026,11 +2026,12 @@ def _setitem_single_column(self, loc: int, value, plane_indexer):
                     "array. To retain the old behavior, use either "
                     "`df[df.columns[i]] = newvals` or, if columns are non-unique, "
                     "`df.isetitem(i, newvals)`",
-                    FutureWarning,
+                    DeprecationWarning,
                     stacklevel=find_stack_level(),
                 )
                 # TODO: how to get future behavior?
                 # TODO: what if we got here indirectly via loc?
+                pass
         return
 
     def _setitem_single_block(self, indexer, value, name: str):

pandas/tests/indexing/test_loc.py

@@ -3211,3 +3211,11 @@ def test_getitem_loc_str_periodindex(self):
         index = pd.period_range(start="2000", periods=20, freq="B")
         series = Series(range(20), index=index)
         assert series.loc["2000-01-14"] == 9
+
+    def test_deprecation_warnings_raised_loc(self):
+        # GH#48673
+        with tm.assert_produces_warning(DeprecationWarning):
+            values = np.arange(4).reshape(2, 2)
+            df = DataFrame(values, columns=["a", "b"])
+            new = np.array([10, 11]).astype(np.int16)
+            df.loc[:, "a"] = new