DEPR: try_cast kwarg in mask, where (#38836)

Author: jbrockmendel

doc/source/whatsnew/v1.3.0.rst

@@ -155,7 +155,7 @@ Deprecations
 - Deprecating allowing scalars passed to the :class:`Categorical` constructor (:issue:`38433`)
 - Deprecated allowing subclass-specific keyword arguments in the :class:`Index` constructor, use the specific subclass directly instead (:issue:`14093`,:issue:`21311`,:issue:`22315`,:issue:`26974`)
 - Deprecated ``astype`` of datetimelike (``timedelta64[ns]``, ``datetime64[ns]``, ``Datetime64TZDtype``, ``PeriodDtype``) to integer dtypes, use ``values.view(...)`` instead (:issue:`38544`)
--
+- Deprecated keyword ``try_cast`` in :meth:`Series.where`, :meth:`Series.mask`, :meth:`DataFrame.where`, :meth:`DataFrame.mask`; cast results manually if desired (:issue:`38836`)
 -
 
 .. ---------------------------------------------------------------------------

pandas/core/generic.py

@@ -8781,7 +8781,6 @@ def _where(
         axis=None,
         level=None,
         errors="raise",
-        try_cast=False,
     ):
         """
         Equivalent to public method `where`, except that `other` is not
@@ -8932,7 +8931,6 @@ def _where(
                 cond=cond,
                 align=align,
                 errors=errors,
-                try_cast=try_cast,
                 axis=block_axis,
             )
             result = self._constructor(new_data)
@@ -8954,7 +8952,7 @@ def where(
         axis=None,
         level=None,
         errors="raise",
-        try_cast=False,
+        try_cast=lib.no_default,
     ):
         """
         Replace values where the condition is {cond_rev}.
@@ -8986,9 +8984,12 @@ def where(
             - 'raise' : allow exceptions to be raised.
             - 'ignore' : suppress exceptions. On error return original object.
 
-        try_cast : bool, default False
+        try_cast : bool, default None
             Try to cast the result back to the input type (if possible).
 
+            .. deprecated:: 1.3.0
+                Manually cast back if necessary.
+
         Returns
         -------
         Same type as caller or None if ``inplace=True``.
@@ -9077,9 +9078,16 @@ def where(
         4  True  True
         """
         other = com.apply_if_callable(other, self)
-        return self._where(
-            cond, other, inplace, axis, level, errors=errors, try_cast=try_cast
-        )
+
+        if try_cast is not lib.no_default:
+            warnings.warn(
+                "try_cast keyword is deprecated and will be removed in a "
+                "future version",
+                FutureWarning,
+                stacklevel=2,
+            )
+
+        return self._where(cond, other, inplace, axis, level, errors=errors)
 
     @final
     @doc(
@@ -9098,12 +9106,20 @@ def mask(
         axis=None,
         level=None,
         errors="raise",
-        try_cast=False,
+        try_cast=lib.no_default,
     ):
 
         inplace = validate_bool_kwarg(inplace, "inplace")
         cond = com.apply_if_callable(cond, self)
 
+        if try_cast is not lib.no_default:
+            warnings.warn(
+                "try_cast keyword is deprecated and will be removed in a "
+                "future version",
+                FutureWarning,
+                stacklevel=2,
+            )
+
         # see gh-21891
         if not hasattr(cond, "__invert__"):
             cond = np.array(cond)
@@ -9114,7 +9130,6 @@ def mask(
             inplace=inplace,
             axis=axis,
             level=level,
-            try_cast=try_cast,
             errors=errors,
         )
 

pandas/core/internals/blocks.py

@@ -1290,9 +1290,7 @@ def _maybe_reshape_where_args(self, values, other, cond, axis):
 
         return other, cond
 
-    def where(
-        self, other, cond, errors="raise", try_cast: bool = False, axis: int = 0
-    ) -> List["Block"]:
+    def where(self, other, cond, errors="raise", axis: int = 0) -> List["Block"]:
         """
         evaluate the block; return result block(s) from the result
 
@@ -1303,7 +1301,6 @@ def where(
         errors : str, {'raise', 'ignore'}, default 'raise'
             - ``raise`` : allow exceptions to be raised
             - ``ignore`` : suppress exceptions. On error return original object
-        try_cast: bool, default False
         axis : int, default 0
 
         Returns
@@ -1342,9 +1339,7 @@ def where(
                 # we cannot coerce, return a compat dtype
                 # we are explicitly ignoring errors
                 block = self.coerce_to_target_dtype(other)
-                blocks = block.where(
-                    orig_other, cond, errors=errors, try_cast=try_cast, axis=axis
-                )
+                blocks = block.where(orig_other, cond, errors=errors, axis=axis)
                 return self._maybe_downcast(blocks, "infer")
 
             if not (
@@ -1825,9 +1820,7 @@ def shift(
             )
         ]
 
-    def where(
-        self, other, cond, errors="raise", try_cast: bool = False, axis: int = 0
-    ) -> List["Block"]:
+    def where(self, other, cond, errors="raise", axis: int = 0) -> List["Block"]:
 
         cond = _extract_bool_array(cond)
         assert not isinstance(other, (ABCIndex, ABCSeries, ABCDataFrame))
@@ -2075,9 +2068,7 @@ def to_native_types(self, na_rep="NaT", **kwargs):
         result = arr._format_native_types(na_rep=na_rep, **kwargs)
         return self.make_block(result)
 
-    def where(
-        self, other, cond, errors="raise", try_cast: bool = False, axis: int = 0
-    ) -> List["Block"]:
+    def where(self, other, cond, errors="raise", axis: int = 0) -> List["Block"]:
         # TODO(EA2D): reshape unnecessary with 2D EAs
         arr = self.array_values().reshape(self.shape)
 
@@ -2086,9 +2077,7 @@ def where(
         try:
             res_values = arr.T.where(cond, other).T
         except (ValueError, TypeError):
-            return super().where(
-                other, cond, errors=errors, try_cast=try_cast, axis=axis
-            )
+            return super().where(other, cond, errors=errors, axis=axis)
 
         # TODO(EA2D): reshape not needed with 2D EAs
         res_values = res_values.reshape(self.values.shape)

pandas/core/internals/managers.py

@@ -542,9 +542,7 @@ def get_axe(block, qs, axes):
     def isna(self, func) -> "BlockManager":
         return self.apply("apply", func=func)
 
-    def where(
-        self, other, cond, align: bool, errors: str, try_cast: bool, axis: int
-    ) -> "BlockManager":
+    def where(self, other, cond, align: bool, errors: str, axis: int) -> "BlockManager":
         if align:
             align_keys = ["other", "cond"]
         else:
@@ -557,7 +555,6 @@ def where(
             other=other,
             cond=cond,
             errors=errors,
-            try_cast=try_cast,
             axis=axis,
         )
 

pandas/tests/frame/indexing/test_mask.py

@@ -83,3 +83,16 @@ def test_mask_dtype_conversion(self):
         expected = bools.astype(float).mask(mask)
         result = bools.mask(mask)
         tm.assert_frame_equal(result, expected)
+
+
+def test_mask_try_cast_deprecated(frame_or_series):
+
+    obj = DataFrame(np.random.randn(4, 3))
+    if frame_or_series is not DataFrame:
+        obj = obj[0]
+
+    mask = obj > 0
+
+    with tm.assert_produces_warning(FutureWarning):
+        # try_cast keyword deprecated
+        obj.mask(mask, -1, try_cast=True)

pandas/tests/frame/indexing/test_where.py

@@ -672,3 +672,15 @@ def test_where_ea_other(self):
         expected["B"] = expected["B"].astype(object)
         result = df.where(mask, ser2, axis=1)
         tm.assert_frame_equal(result, expected)
+
+
+def test_where_try_cast_deprecated(frame_or_series):
+    obj = DataFrame(np.random.randn(4, 3))
+    if frame_or_series is not DataFrame:
+        obj = obj[0]
+
+    mask = obj > 0
+
+    with tm.assert_produces_warning(FutureWarning):
+        # try_cast keyword deprecated
+        obj.where(mask, -1, try_cast=False)