Add Element.__contains__ method (#2330)

doc/Tutorials/Columnar_Data.ipynb

@@ -315,7 +315,7 @@
    "source": [
     "xs = np.arange(10)\n",
     "curve = hv.Curve(zip(xs, np.exp(xs)))\n",
-    "curve * hv.Scatter(zip(xs, curve)) + curve.table()"
+    "curve * hv.Scatter(curve) + curve.table()"
    ]
   },
   {

examples/user_guide/07-Tabular_Datasets.ipynb

@@ -340,7 +340,7 @@
    "source": [
     "xs = np.arange(10)\n",
     "curve = hv.Curve(zip(xs, np.exp(xs)))\n",
-    "curve * hv.Scatter(zip(xs, curve)) + curve.table()"
+    "curve * hv.Scatter(curve) + curve.table()"
    ]
   },
   {

holoviews/core/element.py

@@ -68,6 +68,22 @@ def __nonzero__(self):
         """
         return True
 
+
+    def __contains__(self, dimension):
+        """
+        Allows checking whether a Dimension is in the Elements key or
+        value dimensions.
+        """
+        return dimension in self.dimensions()
+
+
+    def __iter__(self):
+        """
+        Disable iterator interface.
+        """
+        raise NotImplementedError('Iteration on Elements is not supported.')
+
+
     __bool__ = __nonzero__
 
 

tests/core/testelement.py

@@ -0,0 +1,26 @@
+from holoviews.core import Dimension, Element
+from holoviews.element.comparison import ComparisonTestCase
+
+
+class ElementTests(ComparisonTestCase):
+
+    def setUp(self):
+        self.element = Element([], kdims=['A', 'B'], vdims=['C'])
+
+    def test_key_dimension_in_element(self):
+        self.assertTrue(Dimension('A') in self.element)
+
+    def test_value_dimension_in_element(self):
+        self.assertTrue(Dimension('C') in self.element)
+
+    def test_dimension_not_in_element(self):
+        self.assertFalse(Dimension('D') in self.element)
+
+    def test_key_dimension_string_in_element(self):
+        self.assertTrue('A' in self.element)
+
+    def test_value_dimension_string_in_element(self):
+        self.assertTrue('C' in self.element)
+
+    def test_dimension_string_not_in_element(self):
+        self.assertFalse('D' in self.element)