What to do when no variance in weight bounds

swmmanywhere/graph_utilities.py

@@ -1012,6 +1012,12 @@ def __call__(self, G: nx.Graph,
             bounds[w][0] = min(bounds[w][0], d.get(w, np.Inf))
             bounds[w][1] = max(bounds[w][1], d.get(w, -np.Inf))
 
+        # Avoid division by zero
+        for w, bnd in bounds.items():
+            if bnd[0] == bnd[1]:
+                # I guess this shouldn't make a difference what the value is
+                bounds[w][1] += 1e-10 
+
         G = G.copy()
         eps = np.finfo(float).eps
         for u, v, d in G.edges(data=True):

tests/test_graph_utilities.py

@@ -184,7 +184,20 @@ def test_calculate_weights():
     for u, v, data in G.edges(data=True):
         assert 'weight' in data.keys()
         assert math.isfinite(data['weight'])
-
+
+def test_calculate_weights_novar():
+    """Test the calculate_weights function with no variance."""
+    G, _ = load_street_network()
+    params = parameters.TopologyDerivation()
+    for weight in params.weights:
+        for ix, (u,v,data) in enumerate(G.edges(data=True)):
+            data[weight] = 1.5
+
+    G = gu.calculate_weights(G, params)
+    for u, v, data in G.edges(data=True):
+        assert 'weight' in data.keys()
+        assert math.isfinite(data['weight'])
+
 def test_identify_outlets_no_river():
     """Test the identify_outlets in the no river case."""
     G, _ = load_street_network()