wip Series.update pdep6-issue

Author: MarcoGorelli

pandas/core/series.py

@@ -3598,10 +3598,11 @@ def update(self, other: Series | Sequence | Mapping) -> None:
         if not isinstance(other, Series):
             other = Series(other)
 
-        other = other.reindex_like(self)
+        other = other.loc[other.index.isin(self.index)]
         mask = notna(other)
 
-        self._mgr = self._mgr.putmask(mask=mask, new=other)
+        indexer = self.index._get_indexer(other.index[mask])
+        self._set_values(indexer, other[mask]._values)
         self._maybe_update_cacher()
 
     # ----------------------------------------------------------------------

pandas/tests/series/methods/test_update.py

@@ -46,7 +46,7 @@ def test_update(self, using_copy_on_write):
         "other, dtype, expected, warn",
         [
             # other is int
-            ([61, 63], "int32", Series([10, 61, 12], dtype="int32"), None),
+            ([61, 63], "int32", Series([10, 61, 12]), FutureWarning),
             ([61, 63], "int64", Series([10, 61, 12]), None),
             ([61, 63], float, Series([10.0, 61.0, 12.0]), None),
             ([61, 63], object, Series([10, 61, 12], dtype=object), None),
@@ -137,3 +137,10 @@ def test_update_with_categorical_type(self):
         result = s1
         expected = Series(["b", "a", "c"], index=[1, 2, 3], dtype=dtype)
         tm.assert_series_equal(result, expected)
+
+    def test_update_with_bool_type(self):
+        # https://github.com/pandas-dev/pandas/issues/55990
+        s = Series([True, True], index=["a", "b"])
+        s.update({"a": False})
+        expected = Series([False, True], index=["a", "b"])
+        tm.assert_series_equal(s, expected)