whatsnew, GH ref

Author: jbrockmendel

doc/source/whatsnew/v1.4.0.rst

@@ -529,7 +529,7 @@ Other Deprecations
 - Deprecated silent dropping of columns that raised a ``TypeError`` in :class:`Series.transform` and :class:`DataFrame.transform` when used with a dictionary (:issue:`43740`)
 - Deprecated silent dropping of columns that raised a ``TypeError``, ``DataError``, and some cases of ``ValueError`` in :meth:`Series.aggregate`, :meth:`DataFrame.aggregate`, :meth:`Series.groupby.aggregate`, and :meth:`DataFrame.groupby.aggregate` when used with a list (:issue:`43740`)
 - Deprecated casting behavior when setting timezone-aware value(s) into a timezone-aware :class:`Series` or :class:`DataFrame` column when the timezones do not match. Previously this cast to object dtype. In a future version, the values being inserted will be converted to the series or column's existing timezone (:issue:`37605`)
-- Deprecated casting behavior when passing an item with mismatched-timezone to :meth:`DatetimeIndex.insert`, :meth:`DatetimeIndex.putmask`, :meth:`DatetimeIndex.where` :meth:`DatetimeIndex.fillna`, :meth:`Series.mask`, :meth:`Series.where`, :meth:`Series.fillna`, :meth:`Series.shift`, :meth:`Series.replace`, :meth:`Series.reindex` (and :class:`DataFrame` column analogues). In the past this has cast to object dtype. In a future version, these will cast the passed item to the index or series's timezone (:issue:`37605`)
+- Deprecated casting behavior when passing an item with mismatched-timezone to :meth:`DatetimeIndex.insert`, :meth:`DatetimeIndex.putmask`, :meth:`DatetimeIndex.where` :meth:`DatetimeIndex.fillna`, :meth:`Series.mask`, :meth:`Series.where`, :meth:`Series.fillna`, :meth:`Series.shift`, :meth:`Series.replace`, :meth:`Series.reindex` (and :class:`DataFrame` column analogues). In the past this has cast to object dtype. In a future version, these will cast the passed item to the index or series's timezone (:issue:`37605`,:issue:`44940`)
 - Deprecated the 'errors' keyword argument in :meth:`Series.where`, :meth:`DataFrame.where`, :meth:`Series.mask`, and meth:`DataFrame.mask`; in a future version the argument will be removed (:issue:`44294`)
 - Deprecated the ``prefix`` keyword argument in :func:`read_csv` and :func:`read_table`, in a future version the argument will be removed (:issue:`43396`)
 - Deprecated :meth:`PeriodIndex.astype` to ``datetime64[ns]`` or ``DatetimeTZDtype``, use ``obj.to_timestamp(how).tz_localize(dtype.tz)`` instead (:issue:`44398`)
@@ -837,7 +837,7 @@ ExtensionArray
 - Bug in :func:`array` incorrectly raising when passed a ``ndarray`` with ``float16`` dtype (:issue:`44715`)
 - Bug in calling ``np.sqrt`` on :class:`BooleanArray` returning a malformed :class:`FloatingArray` (:issue:`44715`)
 - Bug in :meth:`Series.where` with ``ExtensionDtype`` when ``other`` is a NA scalar incompatible with the series dtype (e.g. ``NaT`` with a numeric dtype) incorrectly casting to a compatible NA value (:issue:`44697`)
--
+- Fixed bug in :meth:`Series.replace` with ``FloatDtype``, ``string[python]``, or ``string[pyarrow]`` dtype not being preserved when possible (:issue:`33484`)
 
 Styler
 ^^^^^^

pandas/tests/frame/methods/test_replace.py

@@ -1387,6 +1387,7 @@ def test_replace_dict_category_type(self):
         Test to ensure category dtypes are maintained
         after replace with dict values
         """
+        # GH#35268, GH#44940
 
         # create input dataframe
         input_dict = {"col1": ["a"], "col2": ["obj1"], "col3": ["cat1"]}

pandas/tests/indexing/test_coercion.py

@@ -1206,7 +1206,7 @@ def test_replace_series_datetime_datetime(self, how, to_key, from_key, replacer)
             and obj.dtype != rep_ser.dtype
         ):
             # mismatched tz DatetimeArray behavior will change to cast
-            #  for setitem-like methods with mismatched tzs
+            #  for setitem-like methods with mismatched tzs GH#44940
             warn = FutureWarning
 
         msg = "explicitly cast to object"

pandas/tests/series/methods/test_replace.py

@@ -159,8 +159,7 @@ def check_replace(to_rep, val, expected):
             tm.assert_series_equal(expected, result)
             tm.assert_series_equal(expected, sc)
 
-        # 3.0 can still be held in our int64 series, so we do not upcast
-        # Note this matches what we get with the scalars 3 and 3.0
+        # 3.0 can still be held in our int64 series, so we do not upcast GH#44940
         tr, v = [3], [3.0]
         check_replace(tr, v, ser)
         # Note this matches what we get with the scalars 3 and 3.0
@@ -260,7 +259,7 @@ def test_replace2(self):
         assert (ser[20:30] == -1).all()
 
     def test_replace_with_dictlike_and_string_dtype(self, nullable_string_dtype):
-        # GH 32621
+        # GH 32621, GH#44940
         ser = pd.Series(["one", "two", np.nan], dtype=nullable_string_dtype)
         expected = pd.Series(["1", "2", np.nan], dtype=nullable_string_dtype)
         result = ser.replace({"one": "1", "two": "2"})
@@ -318,6 +317,7 @@ def test_replace_categorical(self, categorical, numeric):
         expected = pd.Series(numeric).astype("category")
         if 2 not in expected.cat.categories:
             # i.e. categories should be [1, 2] even if there are no "B"s present
+            # GH#44940
             expected = expected.cat.add_categories(2)
         tm.assert_series_equal(expected, result)