switched operator overloading to singledispatch (see issue #4)

graphi/operators/_density.py

@@ -1,8 +1,12 @@
 from __future__ import division
-from . import interface
 
+try:
+    from singledispatch import singledispatch
+except ImportError:
+    from functools import singledispatch
 
-@interface.graph_operator
+
+@singledispatch
 def density(graph):
     """
     Return the density of the graph, i.e. the connectedness of its nodes

graphi/operators/_neighbours.py

@@ -1,7 +1,10 @@
-from . import interface
+try:
+    from singledispatch import singledispatch
+except ImportError:
+    from functools import singledispatch
 
 
-@interface.graph_operator
+@singledispatch
 def neighbours(graph, node, maximum_distance=None):
     """
     Yield all nodes to which there is an outgoing edge from ``node`` in ``graph``

graphi_unittests/operators_unittests/test_neighbours.py

@@ -27,15 +27,19 @@ def test_operator(self):
                     )
                 self.assertEqual(set(neighbours(graph, 'node', float('-inf'))), set())
 
-    def test_method(self):
+    def test_override(self):
         """Overridden neighbours(graph, node, ...)"""
         class NeighboursGraph(adjacency_graph.AdjacencyGraph):
-            def __graphi_neighbours__(self, node, maximum_distance=None):
-                if maximum_distance is None:
-                    return range(len(self[node]))
-                if maximum_distance < 0:
-                    return []
-                return range(int(maximum_distance))
+            pass
+
+        @neighbours.register(NeighboursGraph)
+        def test_neighbours(self, node, maximum_distance=None):
+            if maximum_distance is None:
+                return range(len(self[node]))
+            if maximum_distance < 0:
+                return []
+            return range(int(maximum_distance))
+
         for edges in self._get_edge_values():
             with self.subTest(edges=edges):
                 graph = NeighboursGraph(

setup.py

@@ -23,6 +23,10 @@
     )
 ] if platform.python_implementation() == 'CPython' else []
 
+install_requires = ['six']
+if sys.version_info < (3, 4):
+    install_requires.append('singledispatch')
+
 if __name__ == '__main__':
     setup(
         name=package_about['__title__'],
@@ -34,9 +38,7 @@
         url=package_about['__url__'],
         packages=find_packages(),
         # dependencies
-        install_requires=[
-            'six',
-        ],
+        install_requires=install_requires,
         ext_modules=CEXTENSIONS,
         zip_safe=False,
         # metadata for package search