API: change IntervalIndex.contains to work elementwise

pandas/core/indexes/interval.py

@@ -312,24 +312,18 @@ def __contains__(self, key):
 
     def contains(self, key):
         """
-        return a boolean if this key is IN the index
-
-        We accept / allow keys to be not *just* actual
-        objects.
+        Return a boolean mask whether the key is contained in the Intervals
+        of the index.
 
         Parameters
         ----------
-        key : int, float, Interval
+        key : scalar, Interval
 
         Returns
         -------
-        boolean
+        boolean array
         """
-        try:
-            self.get_loc(key)
-            return True
-        except KeyError:
-            return False
+        return np.array([key in interval for interval in self], dtype='bool')
 
     @classmethod
     def from_breaks(cls, breaks, closed='right', name=None, copy=False):

pandas/tests/indexes/test_interval.py

@@ -564,22 +564,30 @@ def test_contains(self):
         assert Interval(3, 5) not in i
         assert Interval(-1, 0, closed='left') not in i
 
-    def testcontains(self):
+    def test_contains_method(self):
         # can select values that are IN the range of a value
         i = IntervalIndex.from_arrays([0, 1], [1, 2])
 
-        assert i.contains(0.1)
-        assert i.contains(0.5)
-        assert i.contains(1)
-        assert i.contains(Interval(0, 1))
-        assert i.contains(Interval(0, 2))
+        expected = np.array([False, False], dtype='bool')
+        actual = i.contains(0)
+        tm.assert_numpy_array_equal(actual, expected)
+        actual = i.contains(3)
+        tm.assert_numpy_array_equal(actual, expected)
+
+        expected = np.array([True, False], dtype='bool')
+        actual = i.contains(0.5)
+        tm.assert_numpy_array_equal(actual, expected)
+        actual = i.contains(1)
+        tm.assert_numpy_array_equal(actual, expected)
 
-        # these overlaps completely
-        assert i.contains(Interval(0, 3))
-        assert i.contains(Interval(1, 3))
+        # TODO what to do with intervals?
+        # assert i.contains(Interval(0, 1))
+        # assert i.contains(Interval(0, 2))
+        #
+        # # these overlaps completely
+        # assert i.contains(Interval(0, 3))
+        # assert i.contains(Interval(1, 3))
 
-        assert not i.contains(20)
-        assert not i.contains(-20)
 
     def test_dropna(self):