Maintain inplace operation on series

doc/source/whatsnew/v1.1.3.rst

@@ -35,6 +35,7 @@ Fixed regressions
 - Fixed regression in :meth:`Series.__getitem__` incorrectly raising when the input was a frozenset (:issue:`35747`)
 - Fixed regression in :meth:`read_excel` with ``engine="odf"`` caused ``UnboundLocalError`` in some cases where cells had nested child nodes (:issue:`36122`, :issue:`35802`)
 - Fixed regression in :class:`DataFrame` and :class:`Series` comparisons between numeric arrays and strings (:issue:`35700`, :issue:`36377`)
+- Fixed regression where inplace arithmetic operation on :class:`Series` no longer updated parent :class:`DataFrame` (:issue:`36373`)
 - Fixed regression in :meth:`DataFrame.apply` with ``raw=True`` and user-function returning string (:issue:`35940`)
 - Fixed regression when setting empty :class:`DataFrame` column to a :class:`Series` in preserving name of index in frame (:issue:`36527`)
 - Fixed regression in :class:`Period` incorrect value for ordinal over the maximum timestamp (:issue:`36430`)

pandas/core/generic.py

@@ -3373,8 +3373,12 @@ def _maybe_cache_changed(self, item, value) -> None:
         """
         The object has called back to us saying maybe it has changed.
         """
-        loc = self._info_axis.get_loc(item)
-        self._mgr.iset(loc, value)
+        try:
+            loc = self._info_axis.get_loc(item)
+        except KeyError:
+            pass
+        else:
+            self._mgr.iset(loc, value)
 
     @property
     def _is_cached(self) -> bool_t:

pandas/core/ops/methods.py

@@ -93,8 +93,6 @@ def _wrap_inplace_method(method):
 
         def f(self, other):
             result = method(self, other)
-            # Delete cacher
-            self._reset_cacher()
             # this makes sure that we are aligned like the input
             # we are updating inplace so we want to ignore is_copy
             self._update_inplace(

pandas/tests/arithmetic/test_numeric.py

@@ -1317,3 +1317,13 @@ def test_dataframe_div_silenced():
     )
     with tm.assert_produces_warning(None):
         pdf1.div(pdf2, fill_value=0)
+
+
+def test_inplace_arithmetic_operation_on_series_updating_parent_dataframe():
+    # https://github.com/pandas-dev/pandas/issues/36373
+    df = pd.DataFrame({"A": [1, 2, 3]})
+    s = df["A"]
+    s += 1
+    assert s is df["A"]
+    expected = pd.DataFrame({"A": [2, 3, 4]})
+    tm.assert_frame_equal(df, expected)

pandas/tests/indexing/test_loc.py

@@ -888,22 +888,6 @@ def test_identity_slice_returns_new_object(self):
         original_series[:3] = [7, 8, 9]
         assert all(sliced_series[:3] == [7, 8, 9])
 
-    def test_loc_copy_vs_view(self):
-        # GH 15631
-        x = DataFrame(zip(range(3), range(3)), columns=["a", "b"])
-
-        y = x.copy()
-        q = y.loc[:, "a"]
-        q += 2
-
-        tm.assert_frame_equal(x, y)
-
-        z = x.copy()
-        q = z.loc[x.index, "a"]
-        q += 2
-
-        tm.assert_frame_equal(x, z)
-
     def test_loc_uint64(self):
         # GH20722
         # Test whether loc accept uint64 max value as index.