BUG: Fixing DataFrame.Update crashes when NaT present

doc/source/whatsnew/v2.0.0.rst

@@ -376,6 +376,7 @@ Missing
 - Bug in :meth:`Index.equals` raising ``TypeError`` when :class:`Index` consists of tuples that contain ``NA`` (:issue:`48446`)
 - Bug in :meth:`Series.map` caused incorrect result when data has NaNs and defaultdict mapping was used (:issue:`48813`)
 - Bug in :class:`NA` raising a ``TypeError`` instead of return :class:`NA` when performing a binary operation with a ``bytes`` object (:issue:`49108`)
+- Bug in :meth:`DataFrame.update` with overwrite=False raising ``TypeError`` when self has column with ``NaT`` values and column not present in other DataFrame (:issue:`16713`)
 
 MultiIndex
 ^^^^^^^^^^

pandas/core/frame.py

@@ -8190,11 +8190,12 @@ def update(
  if not isinstance(other, DataFrame):
  other = DataFrame(other)
 
- other = other.reindex_like(self)
+ other = other.reindex(self.index)
 
- for col in self.columns:
+ for col in self.columns.intersection(other.columns):
  this = self[col]._values
  that = other[col]._values
+
  if filter_func is not None:
  with np.errstate(all="ignore"):
  mask = ~filter_func(this) | isna(that)

pandas/tests/frame/methods/test_update.py

@@ -166,3 +166,13 @@ def test_update_modify_view(self, using_copy_on_write):
  tm.assert_frame_equal(result_view, df2_orig)
  else:
  tm.assert_frame_equal(result_view, expected)
+
+ def test_update_dt_column_with_NaT_create_column(self):
+ # GH#16713
+ df = DataFrame({"A": [1, None], "B": [pd.NaT, pd.to_datetime("2016-01-01")]})
+ df2 = DataFrame({"A": [2, 3]})
+ df.update(df2, overwrite=False)
+ expected = DataFrame(
+ {"A": [1.0, 3.0], "B": [pd.NaT, pd.to_datetime("2016-01-01")]}
+ )
+ tm.assert_frame_equal(df, expected)