Implement greedy node list colouring.

listcolouring/__init__.py

@@ -72,6 +72,13 @@ def greedy_list_edge_colouring(G):
         G[u][v]["colour"] = first_permissible_or_none(G, u, v) # random.choice(colours)
     return(G)
 
+def greedy_list_node_colouring(G):
+    """Assign the first permissible colour to every node (or None if all permissible
+    colours already used on incident edges)."""
+    for u in G.nodes:
+        G.nodes[u]["colour"] = first_permissible_or_none_node(G, u)
+    return(G)
+
 def print_list_edge_colouring(G):
     """Print assigned colours and lists of permissible colours for all edges in G."""
     for n, nbrs in G.adj.items():

tests/test_greedy-list-node-colouring.py

@@ -0,0 +1,14 @@
+import networkx as nx
+
+import listcolouring
+from listcolouring import greedy_list_node_colouring
+
+def test_greedy_list_node_colouring():
+  G = nx.complete_graph(3)
+  permissible_dict = {0: [0, 1], 1: [1, 2], 2: [2, 3]}
+  nx.set_node_attributes(G, permissible_dict, "permissible")
+  nx.set_node_attributes(G, None, "colour")
+  G = greedy_list_node_colouring(G)
+  assert G.nodes[0]["colour"] == 0
+  assert G.nodes[1]["colour"] == 1
+  assert G.nodes[2]["colour"] == 2