Backport PR #45334 on branch 1.4.x (DEPR: un-deprecate errors kwd reverts #44294)

doc/source/whatsnew/v1.4.0.rst

@@ -614,7 +614,6 @@ Other Deprecations
 - 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`,: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 passing non boolean argument to sort in :func:`concat` (:issue:`41518`)
 - Deprecated passing arguments as positional for :func:`read_fwf` other than ``filepath_or_buffer`` (:issue:`41485`):

pandas/core/frame.py

@@ -10931,7 +10931,7 @@ def where(
         inplace=False,
         axis=None,
         level=None,
-        errors=lib.no_default,
+        errors="raise",
         try_cast=lib.no_default,
     ):
         return super().where(cond, other, inplace, axis, level, errors, try_cast)
@@ -10946,7 +10946,7 @@ def mask(
         inplace=False,
         axis=None,
         level=None,
-        errors=lib.no_default,
+        errors="raise",
         try_cast=lib.no_default,
     ):
         return super().mask(cond, other, inplace, axis, level, errors, try_cast)

pandas/core/generic.py

@@ -9002,22 +9002,14 @@ def _where(
         inplace=False,
         axis=None,
         level=None,
-        errors=lib.no_default,
+        errors="raise",
     ):
         """
         Equivalent to public method `where`, except that `other` is not
         applied as a function even if callable. Used in __setitem__.
         """
         inplace = validate_bool_kwarg(inplace, "inplace")
 
-        if errors is not lib.no_default:
-            warnings.warn(
-                f"The 'errors' keyword in {type(self).__name__}.where and mask is "
-                "deprecated and will be removed in a future version.",
-                FutureWarning,
-                stacklevel=find_stack_level(),
-            )
-
         if axis is not None:
             axis = self._get_axis_number(axis)
 
@@ -9153,7 +9145,7 @@ def where(
         inplace=False,
         axis=None,
         level=None,
-        errors=lib.no_default,
+        errors="raise",
         try_cast=lib.no_default,
     ):
         """
@@ -9186,9 +9178,6 @@ def where(
             - 'raise' : allow exceptions to be raised.
             - 'ignore' : suppress exceptions. On error return original object.
 
-            .. deprecated:: 1.4.0
-                Previously was silently ignored.
-
         try_cast : bool, default None
             Try to cast the result back to the input type (if possible).
 
@@ -9309,7 +9298,7 @@ def mask(
         inplace=False,
         axis=None,
         level=None,
-        errors=lib.no_default,
+        errors="raise",
         try_cast=lib.no_default,
     ):
 

pandas/tests/series/methods/test_fillna.py

@@ -151,18 +151,15 @@ def test_fillna_consistency(self):
         )
         tm.assert_series_equal(result, expected)
 
-        msg = "The 'errors' keyword in "
-        with tm.assert_produces_warning(FutureWarning, match=msg):
-            # where (we ignore the errors=)
-            result = ser.where(
-                [True, False], Timestamp("20130101", tz="US/Eastern"), errors="ignore"
-            )
+        # where (we ignore the errors=)
+        result = ser.where(
+            [True, False], Timestamp("20130101", tz="US/Eastern"), errors="ignore"
+        )
         tm.assert_series_equal(result, expected)
 
-        with tm.assert_produces_warning(FutureWarning, match=msg):
-            result = ser.where(
-                [True, False], Timestamp("20130101", tz="US/Eastern"), errors="ignore"
-            )
+        result = ser.where(
+            [True, False], Timestamp("20130101", tz="US/Eastern"), errors="ignore"
+        )
         tm.assert_series_equal(result, expected)
 
         # with a non-datetime