Add current_key property to DynamicMap

examples/user_guide/07-Live_Data.ipynb

@@ -214,9 +214,36 @@
     "The sliders now snap to the specified dimension values and if you are running this live, the above cell should look like a [HoloMap](../reference/containers/bokeh/HoloMap.ipynb). ``DynamicMap`` is in fact a subclass of ``HoloMap`` with some crucial differences:\n",
     "\n",
     "* You can now pick as many values of **alpha** or **beta** as allowed by the slider.\n",
-    "* What you see in the cell above will not be exported in any HTML snapshot of the notebook\n",
-    "\n",
-    "\n",
+    "* What you see in the cell above will not be exported in any HTML snapshot of the notebook"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "#### Getting the current key"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "The ``current_key`` property returns the current key of the ``DynamicMap``, i.e. either a value (one-dimensional) or a tuple (multi-dimensional) that represents the current state of the widgets. If you move the sliders above and re-execute the cell below you will see that the tuple returned reflects the values of *alpha* and *beta*."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "dmap.current_key"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
     "We will now explore how ``DynamicMaps`` relate to ``HoloMaps`` including conversion operations between the two types. As we will see, there are other ways to display a ``DynamicMap`` without using explicit indexing or redim."
    ]
   },
@@ -657,5 +684,5 @@
   }
  },
  "nbformat": 4,
- "nbformat_minor": 1
+ "nbformat_minor": 4
 }

holoviews/core/spaces.py

@@ -826,6 +826,8 @@ def __init__(self, callback, initial_items=None, streams=None, **params):
 
         self.periodic = periodic(self)
 
+        self._current_key = None
+
     @property
     def opts(self):
         return Opts(self, mode='dynamicmap')
@@ -853,6 +855,11 @@ def unbounded(self):
                 unbounded_dims.append(str(kdim))
         return unbounded_dims
 
+    @property
+    def current_key(self):
+        """Returns the current key value."""
+        return self._current_key
+
     def _stream_parameters(self):
         return util.stream_parameters(
             self.streams, no_duplicates=not self.positional_stream_args
@@ -1170,6 +1177,8 @@ def __getitem__(self, key):
             otherwise returns cloned DynamicMap containing the cross-
             product of evaluated items.
         """
+        self._current_key = key
+
         # Split key dimensions and data slices
         sample = False
         if key is Ellipsis:

holoviews/tests/core/test_dynamic.py

@@ -543,6 +543,36 @@ def test_mixed_kdim_streams_bounded_redim(self):
         self.assertEqual(dmap.redim.range(z=(-0.5,0.5)).unbounded, [])
 
 
+class DynamicMapCurrentKeyProperty(ComparisonTestCase):
+
+    def test_current_key_None_on_init(self):
+        fn = lambda i: Image(sine_array(0,i))
+        dmap = DynamicMap(fn, kdims=[Dimension('dim', range=(0,10))])
+        self.assertIsNone(dmap.current_key)
+
+    def test_current_key_one_dimension(self):
+        fn = lambda i: Image(sine_array(0,i))
+        dmap=DynamicMap(fn, kdims=[Dimension('dim', range=(0,10))])
+        dmap[0]
+        self.assertEqual(dmap.current_key, 0)
+        dmap[1]
+        self.assertEqual(dmap.current_key, 1)
+        dmap[0]
+        self.assertEqual(dmap.current_key, 0)
+        self.assertNotEqual(dmap.current_key, dmap.last_key)
+
+    def test_current_key_multiple_dimensions(self):
+        fn = lambda i, j: Curve([i, j])
+        dmap=DynamicMap(fn, kdims=[Dimension('i', range=(0,5)), Dimension('j', range=(0,5))])
+        dmap[0, 2]
+        self.assertEqual(dmap.current_key, (0, 2))
+        dmap[5, 5]
+        self.assertEqual(dmap.current_key, (5, 5))
+        dmap[0, 2]
+        self.assertEqual(dmap.current_key, (0, 2))
+        self.assertNotEqual(dmap.current_key, dmap.last_key)
+
+
 class DynamicTransferStreams(ComparisonTestCase):
 
     def setUp(self):