Fix bug GH23823

Author: makbigc

doc/source/whatsnew/v0.25.0.rst

@@ -105,7 +105,7 @@ Performance Improvements
 Bug Fixes
 ~~~~~~~~~
 
--
+- :func:`maybe_upcast_putmask` does not replace the element of the ``ndarray`` correctly (:issue:`23823`)
 
 Categorical
 ^^^^^^^^^^^

pandas/core/dtypes/cast.py

@@ -209,7 +209,10 @@ def changeit():
                 om = other[mask]
                 om_at = om.astype(result.dtype)
                 if (om == om_at).all():
-                    new_result = result.values.copy()
+                    if isinstance(result, np.ndarray):
+                        new_result = result.copy()
+                    else:
+                        new_result = result.values.copy()
                     new_result[mask] = om_at
                     result[:] = new_result
                     return result, False

pandas/tests/dtypes/cast/test_upcast.py

@@ -0,0 +1,28 @@
+# -*- coding: utf-8 -*-
+
+import numpy as np
+
+from pandas.core.dtypes.cast import maybe_upcast_putmask
+
+from pandas import Series
+from pandas.util import testing as tm
+
+
+def test_upcast_series():
+    result = Series([10, 11, 12])
+    mask = Series([False, True, False])
+    other = Series([np.nan, 61, np.nan])
+    expected = Series([10, 61, 12])
+
+    result, _ = maybe_upcast_putmask(result, mask, other)
+    tm.assert_series_equal(result, expected)
+
+
+def test_upcast_np_array():
+    result = np.array([10, 11, 12])
+    mask = np.array([False, True, False])
+    other = np.array([np.nan, 61, np.nan])
+    expected = np.array([10, 61, 12])
+
+    result, _ = maybe_upcast_putmask(result, mask, other)
+    tm.assert_numpy_array_equal(result, expected)