Merge branch 'master' into fix-crosstab-cats

Author: simonjayhawkins

doc/source/whatsnew/v1.1.4.rst

@@ -28,8 +28,10 @@ Fixed regressions
 - Fixed regression in certain offsets (:meth:`pd.offsets.Day() <pandas.tseries.offsets.Day>` and below) no longer being hashable (:issue:`37267`)
 - Fixed regression in :class:`StataReader` which required ``chunksize`` to be manually set when using an iterator to read a dataset (:issue:`37280`)
 - Fixed regression in setitem with :meth:`DataFrame.iloc` which raised error when trying to set a value while filtering with a boolean list (:issue:`36741`)
+- Fixed regression in setitem with a Series getting aligned before setting the values (:issue:`37427`)
 - Fixed regression in :attr:`MultiIndex.is_monotonic_increasing` returning wrong results with ``NaN`` in at least one of the levels (:issue:`37220`)
 - Fixed regression in :meth:`crosstab` that failed when the input series are categorical. (:issue:`37465`)
+- Fixed regression in inplace arithmetic operation on a Series not updating the parent DataFrame (:issue:`36373`)
 
 .. ---------------------------------------------------------------------------
 

pandas/core/generic.py

@@ -11115,6 +11115,11 @@ def _inplace_method(self, other, op):
         """
         result = op(self, other)
 
+        if self.ndim == 1 and result._indexed_same(self) and result.dtype == self.dtype:
+            # GH#36498 this inplace op can _actually_ be inplace.
+            self._values[:] = result._values
+            return self
+
         # Delete cacher
         self._reset_cacher()
 

pandas/core/series.py

@@ -1048,10 +1048,8 @@ def _set_with_engine(self, key, value):
     def _set_with(self, key, value):
         # other: fancy integer or otherwise
         if isinstance(key, slice):
-            # extract_array so that if we set e.g. ser[-5:] = ser[:5]
-            #  we get the first five values, and not 5 NaNs
             indexer = self.index._convert_slice_indexer(key, kind="getitem")
-            self.iloc[indexer] = extract_array(value, extract_numpy=True)
+            return self._set_values(indexer, value)
 
         else:
             assert not isinstance(key, tuple)
@@ -1069,12 +1067,28 @@ def _set_with(self, key, value):
             #  should be caught by the is_bool_indexer check in __setitem__
             if key_type == "integer":
                 if not self.index._should_fallback_to_positional():
-                    self.loc[key] = value
+                    self._set_labels(key, value)
                 else:
-                    self.iloc[key] = value
+                    self._set_values(key, value)
             else:
                 self.loc[key] = value
 
+    def _set_labels(self, key, value):
+        key = com.asarray_tuplesafe(key)
+        indexer: np.ndarray = self.index.get_indexer(key)
+        mask = indexer == -1
+        if mask.any():
+            raise KeyError(f"{key[mask]} not in index")
+        self._set_values(indexer, value)
+
+    def _set_values(self, key, value):
+        if isinstance(key, Series):
+            key = key._values
+        self._mgr = self._mgr.setitem(  # type: ignore[assignment]
+            indexer=key, value=value
+        )
+        self._maybe_update_cacher()
+
     def _set_value(self, label, value, takeable: bool = False):
         """
         Quickly set single value at passed label.

pandas/tests/frame/test_arithmetic.py

@@ -1698,3 +1698,16 @@ def test_arith_list_of_arraylike_raise(to_add):
         df + to_add
     with pytest.raises(ValueError, match=msg):
         to_add + df
+
+
+def test_inplace_arithmetic_series_update():
+    # https://github.com/pandas-dev/pandas/issues/36373
+    df = DataFrame({"A": [1, 2, 3]})
+    series = df["A"]
+    vals = series._values
+
+    series += 1
+    assert series._values is vals
+
+    expected = DataFrame({"A": [2, 3, 4]})
+    tm.assert_frame_equal(df, expected)

pandas/tests/indexing/test_loc.py

@@ -888,6 +888,7 @@ def test_identity_slice_returns_new_object(self):
         original_series[:3] = [7, 8, 9]
         assert all(sliced_series[:3] == [7, 8, 9])
 
+    @pytest.mark.xfail(reason="accidental fix reverted - GH37497")
     def test_loc_copy_vs_view(self):
         # GH 15631
         x = DataFrame(zip(range(3), range(3)), columns=["a", "b"])

pandas/tests/series/indexing/test_getitem.py

@@ -290,3 +290,13 @@ def test_getitem_multilevel_scalar_slice_not_implemented(
     msg = r"\(2000, slice\(3, 4, None\)\)"
     with pytest.raises(TypeError, match=msg):
         ser[2000, 3:4]
+
+
+def test_getitem_assignment_series_aligment():
+    # https://github.com/pandas-dev/pandas/issues/37427
+    # with getitem, when assigning with a Series, it is not first aligned
+    s = Series(range(10))
+    idx = np.array([2, 4, 9])
+    s[idx] = Series([10, 11, 12])
+    expected = Series([0, 1, 10, 3, 11, 5, 6, 7, 8, 12])
+    tm.assert_series_equal(s, expected)