BUG: Fix Series.isin with date/time-like dtypes (GH5021)

doc/source/release.rst

@@ -633,6 +633,7 @@ Bug Fixes
   - Fixed issue with ``drop`` and a non-unique index on Series (:issue:`5248`)
   - Fixed seg fault in C parser caused by passing more names than columns in
     the file. (:issue:`5156`)
+  - Fix ``Series.isin`` with date/time-like dtypes (:issue:`5021`)
 
 pandas 0.12.0
 -------------

pandas/core/series.py

@@ -2077,8 +2077,20 @@ def isin(self, values):
             raise TypeError("only list-like objects are allowed to be passed"
                             " to Series.isin(), you passed a "
                             "{0!r}".format(type(values).__name__))
+
+        # may need i8 conversion for proper membership testing
+        comps = _values_from_object(self)
+        if com.is_datetime64_dtype(self):
+            from pandas.tseries.tools import to_datetime
+            values = Series(to_datetime(values)).values.view('i8')
+            comps = comps.view('i8')
+        elif com.is_timedelta64_dtype(self):
+            from pandas.tseries.timedeltas import to_timedelta
+            values = Series(to_timedelta(values)).values.view('i8')
+            comps = comps.view('i8')
+
         value_set = set(values)
-        result = lib.ismember(_values_from_object(self), value_set)
+        result = lib.ismember(comps, value_set)
         return self._constructor(result, index=self.index).__finalize__(self)
 
     def between(self, left, right, inclusive=True):

pandas/tests/test_series.py

@@ -4840,7 +4840,7 @@ def test_isin(self):
         assert_series_equal(result, expected)
 
     def test_isin_with_string_scalar(self):
-        #GH4763
+        # GH4763
         s = Series(['A', 'B', 'C', 'a', 'B', 'B', 'A', 'C'])
         with tm.assertRaises(TypeError):
             s.isin('a')
@@ -4849,6 +4849,38 @@ def test_isin_with_string_scalar(self):
             s = Series(['aaa', 'b', 'c'])
             s.isin('aaa')
 
+    def test_isin_with_i8(self):
+        # GH 5021
+
+        expected = Series([True,True,False,False,False])
+        expected2 = Series([False,True,False,False,False])
+
+        # datetime64[ns]
+        s = Series(date_range('jan-01-2013','jan-05-2013'))
+
+        result = s.isin(s[0:2])
+        assert_series_equal(result, expected)
+
+        result = s.isin(s[0:2].values)
+        assert_series_equal(result, expected)
+
+        # fails on dtype conversion in the first place
+        if not _np_version_under1p7:
+            result = s.isin(s[0:2].values.astype('datetime64[D]'))
+            assert_series_equal(result, expected)
+
+        result = s.isin([s[1]])
+        assert_series_equal(result, expected2)
+
+        result = s.isin([np.datetime64(s[1])])
+        assert_series_equal(result, expected2)
+
+        # timedelta64[ns]
+        if not _np_version_under1p7:
+            s = Series(pd.to_timedelta(lrange(5),unit='d'))
+            result = s.isin(s[0:2])
+            assert_series_equal(result, expected)
+
 #------------------------------------------------------------------------------
 # TimeSeries-specific
     def test_cummethods_bool(self):