docs

Author: jreback

doc/source/whatsnew/v0.21.0.txt

@@ -59,13 +59,58 @@ Backwards incompatible API changes
 Dtype Conversions
 ^^^^^^^^^^^^^^^^^
 
-Example about setitem / where with bools.
+- Previously assignments, ``.where()`` and ``.fillna()`` with a ``bool`` assignment, would coerce to
+  same type (e.g. int / float), or raise for datetimelikes. These will now preseve the bools with ``object`` dtypes. (:issue:`16821`).
 
+   .. ipython:: python
 
+      s = Series([1, 2, 3])
 
-- Inconsistent behavior in ``.where()`` with datetimelikes which would raise rather than coerce to ``object`` (:issue:`16402`)
-- Bug in assignment against datetime-like data with ``int`` may incorrectly convert to datetime-like (:issue:`14145`)
-- Bug in assignment against ``int64`` data with ``np.ndarray`` with ``float64`` dtype may keep ``int64`` dtype (:issue:`14001`)
+   .. code-block:: python
+
+      In [5]: s[1] = True
+
+      In [6]: s
+      Out[6]:
+      0    1
+      1    1
+      2    3
+      dtype: int64
+
+   New Behavior
+
+   .. ipython:: python
+
+      s[1] = True
+      s
+
+- Previously as assignment to a datetimelike with a non-datetimelike would corece (:issue:`14145`).
+
+   .. ipython:: python
+
+      s = pd.Series([pd.Timestamp('2011-01-01'), pd.Timestamp('2012-01-01')])
+
+   .. code-block:: python
+
+      In [1]: s[1] = 1
+
+      In [2]: s
+      Out[2]:
+      0   2011-01-01 00:00:00.000000000
+      1   1970-01-01 00:00:00.000000001
+      dtype: datetime64[ns]
+
+   These now coerce to ``object`` dtype.
+
+   .. ipython:: python
+
+      s[1] = 1
+      s
+
+- Additional bug fixes w.r.t. dtype conversions.
+
+  - Inconsistent behavior in ``.where()`` with datetimelikes which would raise rather than coerce to ``object`` (:issue:`16402`)
+   - Bug in assignment against ``int64`` data with ``np.ndarray`` with ``float64`` dtype may keep ``int64`` dtype (:issue:`14001`)
 
 .. _whatsnew_0210.api: