Param values stream

holoviews/streams.py

@@ -223,3 +223,60 @@ class PositionXY(Stream):
     def __init__(self, preprocessors=[], source=None, subscribers=[], **params):
         super(PositionXY, self).__init__(preprocessors=preprocessors, source=source,
                                         subscribers=subscribers, **params)
+
+
+
+
+class ParamValues(Stream):
+    """
+    A Stream based on the parameter values of some other parameterized
+    object, whether it is a parameterized class or a parameterized
+    instance.
+
+    The update method enables the stream to update the parameters of the
+    specified object.
+    """
+
+    def __init__(self, obj, **params):
+        self._obj = obj
+        super(ParamValues, self).__init__(**params)
+
+
+    @property
+    def value(self):
+        if isinstance(self._obj, type):
+            remapped={k: getattr(self._obj,k)
+                               for k in self._obj.params().keys() if k!= 'name'}
+        else:
+            remapped={k:v for k,v in self._obj.get_param_values() if k!= 'name'}
+
+        for preprocessor in self.preprocessors:
+            remapped = preprocessor(remapped)
+        return remapped
+
+
+    def update(self, trigger=True, **kwargs):
+        """
+        The update method updates the parameters of the specified object.
+
+        If trigger is enabled, the trigger classmethod is invoked on
+        this Stream instance to execute its subscribers.
+        """
+        if isinstance(self._obj, type):
+            for name in self._obj.params().keys():
+                if name in kwargs:
+                    setattr(self._obj, name, kwargs[name])
+        else:
+            self._obj.set_param(**kwargs)
+
+        if trigger:
+            self.trigger([self])
+
+
+    def __repr__(self):
+        cls_name = self.__class__.__name__
+        return '%s(%r)' % (cls_name, self._obj)
+
+
+    def __str__(self):
+        return repr(self)

tests/teststreams.py

@@ -1,8 +1,9 @@
 """
 Unit test of the streams system
 """
+import param
 from holoviews.element.comparison import ComparisonTestCase
-from holoviews.streams import Stream, PositionX, PositionY, PositionXY
+from holoviews.streams import Stream, PositionX, PositionY, PositionXY, ParamValues
 from holoviews.streams import Rename, Group
 
 
@@ -40,6 +41,44 @@ def test_positionY_const_parameter(self):
             self.assertEqual(str(e), "Constant parameter 'y' cannot be modified")
 
 
+class TestParamValuesStream(ComparisonTestCase):
+
+    def setUp(self):
+
+        class Inner(param.Parameterized):
+
+            x = param.Number(default = 0)
+            y = param.Number(default = 0)
+
+        self.inner = Inner
+
+    def tearDown(self):
+        self.inner.x = 0
+        self.inner.y = 0
+
+    def test_object_value(self):
+        obj = self.inner()
+        stream = ParamValues(obj)
+        self.assertEqual(stream.value, {'x':0, 'y':0})
+
+    def test_class_value(self):
+        stream = ParamValues(self.inner)
+        self.assertEqual(stream.value, {'x':0, 'y':0})
+
+    def test_object_value_update(self):
+        obj = self.inner()
+        stream = ParamValues(obj)
+        self.assertEqual(stream.value, {'x':0, 'y':0})
+        stream.update(x=5, y=10)
+        self.assertEqual(stream.value, {'x':5, 'y':10})
+
+    def test_class_value_update(self):
+        stream = ParamValues(self.inner)
+        self.assertEqual(stream.value, {'x':0, 'y':0})
+        stream.update(x=5, y=10)
+        self.assertEqual(stream.value, {'x':5, 'y':10})
+
+
 
 class TestSubscribers(ComparisonTestCase):