Graph.node interface

2 files changed, 21 insertions, 0 deletions

diff --git a/bsfs/graph/graph.py b/bsfs/graph/graph.py
index 87f7a31..b7b9f1c 100644
--- a/bsfs/graph/graph.py
+++ b/bsfs/graph/graph.py
@@ -99,4 +99,15 @@ class Graph():
         # NOTE: Nodes constructor materializes guids.
         return _nodes.Nodes(self._backend, self._user, type_, guids)
 
+    def node(self, node_type: URI, guid: URI) -> _nodes.Nodes:
+        """Return node *guid* of type *node_type* as a `bsfs.graph.Nodes` instance.
+
+        Note that the *guids* need not to exist (however, the *node_type* has
+        to be part of the schema). An inexistent guid will be created (using
+        *node_type*) once some data is assigned to them.
+
+        """
+        type_ = self.schema.node(node_type)
+        return _nodes.Nodes(self._backend, self._user, type_, {guid})
+
 ## EOF ##
diff --git a/test/graph/test_graph.py b/test/graph/test_graph.py
index f8e107d..33cf6aa 100644
--- a/test/graph/test_graph.py
+++ b/test/graph/test_graph.py
@@ -74,6 +74,16 @@ class TestGraph(unittest.TestCase):
         self.assertEqual(graph.schema, self.backend.schema)
         self.assertRaises(AttributeError, setattr, graph, 'schema', None)
 
+    def test_node(self):
+        graph = Graph(self.backend, self.user)
+        guid = URI('http://example.com/me/entity#1234')
+        # returns a Nodes instance
+        self.assertEqual(
+            graph.node(ns.bsfs.Entity, guid),
+            Nodes(self.backend, self.user, graph.schema.node(ns.bsfs.Entity), {guid}))
+        # node_type must be in the schema
+        self.assertRaises(KeyError, graph.node, ns.bsfs.Invalid, guid)
+
     def test_nodes(self):
         graph = Graph(self.backend, self.user)
         guids = {URI('http://example.com/me/entity#1234'), URI('http://example.com/me/entity#4321')}