BUG: Rows are not inserted into DataFrame from lists of one element i…

doc/source/whatsnew/v2.0.3.rst

@@ -14,7 +14,7 @@ including other versions of pandas.
 Fixed regressions
 ~~~~~~~~~~~~~~~~~
 - Fixed performance regression in merging on datetime-like columns (:issue:`53231`)
--
+- Fixed regression in :meth:`DataFrame.loc` rows are not inserted into DataFrame from lists of one element (:issue:`52825`)
 
 .. ---------------------------------------------------------------------------
 .. _whatsnew_203.bug_fixes:

pandas/core/indexing.py

@@ -2024,10 +2024,18 @@ def _setitem_single_column(self, loc: int, value, plane_indexer) -> None:
 
         is_null_setter = com.is_empty_slice(pi) or is_array_like(pi) and len(pi) == 0
 
+        is_empty_df_setter = com.is_null_slice(pi) and len(self.obj) == 0
+
         if is_null_setter:
             # no-op, don't cast dtype later
             return
 
+        elif is_empty_df_setter:
+            # If we're setting a column to an empty df with null slice,
+            # we shouldn't do it inplace.
+            # GH#52825
+            self.obj.isetitem(loc, value)
+
         elif is_full_setter:
             try:
                 self.obj._mgr.column_setitem(

pandas/tests/indexing/test_indexing.py

@@ -631,6 +631,17 @@ def test_index_type_coercion(self, indexer):
             indexer(s2)["0"] = 0
             assert is_object_dtype(s2.index)
 
+    def test_setitem_one_element_list(self):
+        # GH#52825
+        x_values = ["x_value"]
+        y_values = ["y_value"]
+        df = DataFrame(columns=["x", "y"])
+        df.loc[:, "x"] = x_values
+        df.loc[:, "y"] = y_values
+
+        expected = DataFrame({"x": ["x_value"], "y": ["y_value"]})
+        tm.assert_frame_equal(df, expected)
+
 
 class TestMisc:
     def test_float_index_to_mixed(self):

pandas/tests/indexing/test_loc.py

@@ -614,18 +614,16 @@ def test_loc_setitem_consistency_single_row(self):
 
     def test_loc_setitem_consistency_empty(self):
         # empty (essentially noops)
-        # before the enforcement of #45333 in 2.0, the loc.setitem here would
-        #  change the dtype of df.x to int64
+        # the loc.setitem here changes the dtype of df.x to int64
         expected = DataFrame(columns=["x", "y"])
+        expected["x"] = expected["x"].astype(np.int64)
         df = DataFrame(columns=["x", "y"])
         with tm.assert_produces_warning(None):
             df.loc[:, "x"] = 1
         tm.assert_frame_equal(df, expected)
 
-        # setting with setitem swaps in a new array, so changes the dtype
         df = DataFrame(columns=["x", "y"])
         df["x"] = 1
-        expected["x"] = expected["x"].astype(np.int64)
         tm.assert_frame_equal(df, expected)
 
     def test_loc_setitem_consistency_slice_column_len(self):