BUG : bug in setting a slice of a Series with a np.timedelta64

closes pandas-dev#14155
closes pandas-dev#14160

Author: Russell Smith

doc/source/whatsnew/v0.19.0.txt

@@ -1527,6 +1527,7 @@ Bug Fixes
 - Bug in invalid datetime parsing in ``to_datetime`` and ``DatetimeIndex`` may raise ``TypeError`` rather than ``ValueError`` (:issue:`11169`, :issue:`11287`)
 - Bug in ``Index`` created with tz-aware ``Timestamp`` and mismatched ``tz`` option incorrectly coerces timezone (:issue:`13692`)
 - Bug in ``DatetimeIndex`` with nanosecond frequency does not include timestamp specified with ``end`` (:issue:`13672`)
+- Bug in ```Series``` when setting a slice with a ```np.timedelta64``` (:issue:`14155`)
 
 - Bug in ``Index`` raises ``OutOfBoundsDatetime`` if ``datetime`` exceeds ``datetime64[ns]`` bounds, rather than coercing to ``object`` dtype (:issue:`13663`)
 - Bug in ``Index`` may ignore specified ``datetime64`` or ``timedelta64`` passed as ``dtype``  (:issue:`13981`)

pandas/core/internals.py

@@ -1696,7 +1696,7 @@ def _try_coerce_args(self, values, other):
             other = other.value
         elif isinstance(other, np.timedelta64):
             other_mask = isnull(other)
-            other = other.view('i8')
+            other = Timedelta(other).value
         elif isinstance(other, timedelta):
             other = Timedelta(other).value
         elif isinstance(other, np.ndarray):

pandas/tests/series/test_indexing.py

@@ -1324,6 +1324,13 @@ def test_timedelta_assignment(self):
         s.loc['A'] = timedelta(1)
         tm.assert_series_equal(s, expected)
 
+        # GH 14155
+        s = Series(10 * [np.timedelta64(10, 'm')])
+        s.loc[[1, 2, 3]] = np.timedelta64(20, 'm')
+        expected = pd.Series(10 * [np.timedelta64(10, 'm')])
+        expected.loc[[1, 2, 3]] = pd.Timedelta(np.timedelta64(20, 'm'))
+        tm.assert_series_equal(s, expected)
+
     def test_underlying_data_conversion(self):
 
         # GH 4080