Removes self-looped (zero-length) edges if encountered in `nX_simple_…

…geoms`.

cityseer/tools/graphs.py

@@ -56,10 +56,18 @@ def _process_node(n):
         return x, y
 
     # unpack coordinates and build simple edge geoms
+    remove_edges = []
     for s, e, k in tqdm(g_multi_copy.edges(keys=True), disable=checks.quiet_mode):
         s_x, s_y = _process_node(s)
         e_x, e_y = _process_node(e)
-        g_multi_copy[s][e][k]['geom'] = geometry.LineString([[s_x, s_y], [e_x, e_y]])
+        g = geometry.LineString([[s_x, s_y], [e_x, e_y]])
+        if s == e and g.length == 0:
+            remove_edges.append((s, e, k))
+        else:
+            g_multi_copy[s][e][k]['geom'] = g
+    for s, e, k in remove_edges:
+        logger.warning(f'Found zero length looped edge for node {s}, removing from graph.')
+        g_multi_copy.remove_edge(s, e, key=k)
 
     return g_multi_copy
 

setup.py

@@ -6,7 +6,7 @@
 
 setup(
     name='cityseer',
-    version='1.0.4',
+    version='1.0.5',
     packages=['cityseer', 'cityseer.algos', 'cityseer.metrics', 'cityseer.tools'],
     description='Computational tools for urban analysis',
     url='https://github.com/benchmark-urbanism/cityseer-api',

tests/tools/test_graphs.py

@@ -6,26 +6,36 @@
 from cityseer.algos import checks
 from cityseer.metrics import networks, layers
 from cityseer.tools import mock, graphs
-from cityseer.tools.mock import primal_graph, diamond_graph
+from cityseer.tools.mock import mock_graph, primal_graph, diamond_graph
 
 
-def test_nX_simple_geoms(primal_graph):
-    for s, e, k in primal_graph.edges(keys=True):
+def test_nX_simple_geoms():
+    g_raw = mock_graph()
+    # primal_graph already has simple geoms added, so use raw mock_graph instead
+    g_simple = graphs.nX_simple_geoms(g_raw)
+    for s, e, k in g_simple.edges(keys=True):
         line_geom = geometry.LineString([
-            [primal_graph.nodes[s]['x'], primal_graph.nodes[s]['y']],
-            [primal_graph.nodes[e]['x'], primal_graph.nodes[e]['y']]
+            [g_raw.nodes[s]['x'], g_raw.nodes[s]['y']],
+            [g_raw.nodes[e]['x'], g_raw.nodes[e]['y']]
         ])
-        assert line_geom == primal_graph[s][e][k]['geom']
+        assert line_geom == g_simple[s][e][k]['geom']
 
     # check that missing node keys throw an error
+    g_copy = g_raw.copy()
     for k in ['x', 'y']:
-        for n in primal_graph.nodes():
+        for n in g_copy.nodes():
             # delete key from first node and break
-            del primal_graph.nodes[n][k]
+            del g_copy.nodes[n][k]
             break
         # check that missing key throws an error
         with pytest.raises(KeyError):
-            graphs.nX_simple_geoms(primal_graph)
+            graphs.nX_simple_geoms(g_copy)
+
+    # check that zero length self-loops are caught and removed
+    g_copy = g_raw.copy()
+    g_copy.add_edge(0, 0)  # simple geom from self edge = length of zero
+    g_simple = graphs.nX_simple_geoms(g_copy)
+    assert not g_simple.has_edge(0, 0)
 
 
 def test_add_node(diamond_graph):