Allow shortest path solving with no weights for faster performance wh…

…en lengths are not important

tests/test_functions.py

@@ -404,6 +404,15 @@ def test_get_shortest_edge_mixed_keys():
     assert res[0] == "A"
 
 
+def test_get_shortest_edge_no_length():
+    edges = {
+        "A": {"EDGE_ID": "A", "LEN_": 100, "NODEID_FROM": 1, "NODEID_TO": 2},
+        "B": {"EDGE_ID": "B", "LEN_": 20, "NODEID_FROM": 2, "NODEID_TO": 3},
+    }
+    res = functions.get_shortest_edge(edges, length_field=None)
+    assert res[0] == "A"
+
+
 def test_get_unique_ordered_list():
     lst = [2, 2, 1, 1, 4, 4, 1, 2, 3]
     res = functions.get_unique_ordered_list(lst)
@@ -470,7 +479,6 @@ def test_has_no_overlaps_loop_with_split():
 
 
 def test_add_edge():
-
     net = networkx.MultiGraph()
     edge = Edge(0, 1, "A", {"EDGE_ID": 1, "OFFSET": 5, "LEN_": 10})
     functions.add_edge(net, edge.start_node, edge.end_node, edge.key, edge.attributes)
@@ -495,7 +503,6 @@ def test_add_single_edge():
 
 
 def test_remove_edge():
-
     net = networkx.MultiGraph()
     edge = Edge(0, 1, "A", {"EDGE_ID": 1, "OFFSET": 5, "LEN_": 10})
     net.add_edge(edge.start_node, edge.end_node, edge.key, **edge.attributes)
@@ -505,7 +512,6 @@ def test_remove_edge():
 
 
 def test_remove_edge_and_key():
-
     net = loader.create_graph()
     edge = Edge(0, 1, "A", {"EDGE_ID": 1, "OFFSET": 5, "LEN_": 10})
     functions.add_edge(net, **edge._asdict())
@@ -517,7 +523,6 @@ def test_remove_edge_and_key():
 
 
 def test_remove_edge_by_key():
-
     net = loader.create_graph()
     edge = Edge(0, 1, "A", {"EDGE_ID": 1, "OFFSET": 5, "LEN_": 10})
     functions.add_edge(net, **edge._asdict())
@@ -561,6 +566,7 @@ def test_doctest():
     # test_remove_edge()
     # test_remove_edge_and_key()
     # test_remove_edge_by_key()
-    test_add_edge_shorthand()
-    test_add_single_edge()
+    # test_add_edge_shorthand()
+    # test_add_single_edge()
+    test_get_shortest_edge_no_length()
     print("Done!")

tests/test_routing.py

@@ -11,21 +11,18 @@
 
 
 def test_solve_all_simple_paths():
-
     net = networks.simple_network()
     simple_paths = routing.solve_all_simple_paths(net, 1, 5)
     assert list(simple_paths) == [[1, 2, 3, 4, 5]]
 
 
 def test_solve_all_simple_paths_no_node():
-
     net = networks.simple_network()
     with pytest.raises(NodeNotFound):
         list(routing.solve_all_simple_paths(net, 1, 99))
 
 
 def test_solve_all_simple_paths_cutoff():
-
     net = networks.simple_network()
     simple_paths = routing.solve_all_simple_paths(net, 1, 5, cutoff=3)
     assert list(simple_paths) == []
@@ -36,15 +33,13 @@ def test_solve_all_simple_paths_cutoff():
 
 
 def test_solve_all_shortest_paths():
-
     net = networks.circle_network()
     all_paths = routing.solve_all_shortest_paths(net, 1, 3)
     # print(list(all_paths))
     assert list(all_paths) == [[1, 2, 3], [1, 4, 3]]
 
 
 def test_solve_all_shortest_paths_no_node():
-
     net = networks.circle_network()
     # it seems NetworkXNoPath is raised rather than NodeNotFound
     # when using all_shortest_paths in networkx
@@ -54,31 +49,34 @@ def test_solve_all_shortest_paths_no_node():
 
 
 def test_get_path_ends():
-
     edges = [Edge(0, 1, 1, {}), Edge(1, 2, 1, {})]
     ends = routing.get_path_ends(edges)
     # print(ends)
     assert ends == (0, 2)
 
 
 def test_get_path_ends_single_edge():
-
     edges = [Edge(0, 1, 1, {})]
     ends = routing.get_path_ends(edges)
     # print(ends)
     assert ends == (0, 1)
 
 
 def test_solve_shortest_path():
-
     net = networks.simple_network()
     edges = routing.solve_shortest_path(net, start_node=1, end_node=5)
     edge_ids = [edge.key for edge in edges]
     assert edge_ids == [1, 2, 3, 4]
 
 
-def test_solve_shortest_path_directions():
+def test_solve_shortest_path_no_weight():
+    net = networks.simple_network()
+    edges = routing.solve_shortest_path(net, start_node=1, end_node=5, weight=None)
+    edge_ids = [edge.key for edge in edges]
+    assert edge_ids == [1, 2, 3, 4]
 
+
+def test_solve_shortest_path_directions():
     net = networks.simple_network()
     edges = routing.solve_shortest_path(net, start_node=1, end_node=5)
 
@@ -92,7 +90,6 @@ def test_solve_shortest_path_directions():
 
 
 def test_solve_shortest_path_split_network():
-
     net = networks.simple_network()
 
     splitter.split_network_edge(net, 3, [2, 8])
@@ -122,12 +119,13 @@ def test_doctest():
 if __name__ == "__main__":
     logging.basicConfig(level=logging.DEBUG)
     # test_doctest()
-    test_solve_all_simple_paths_no_node()
+    # test_solve_all_simple_paths_no_node()
     # test_solve_all_simple_paths_cutoff()
     # test_solve_all_shortest_paths()
     # test_solve_all_shortest_paths_no_node()
     # test_get_path_ends()
     # test_get_path_ends_single_edge()
     # test_solve_shortest_path_directions()
     # test_solve_shortest_path_split_network()
+    test_solve_shortest_path_no_weight()
     print("Done!")

wayfarer/functions.py

@@ -343,8 +343,8 @@ def get_all_paths_from_nodes(net, node_list, with_direction_flag=False):
     return itertools.chain(*all_paths)
 
 
-def get_path_length(path_edges):
-    return sum([edge.attributes[LENGTH_FIELD] for edge in path_edges])
+def get_path_length(path_edges, length_field: str = LENGTH_FIELD):
+    return sum([edge.attributes[length_field] for edge in path_edges])
 
 
 def get_edges_from_node_pair(
@@ -380,7 +380,7 @@ def get_edges_from_nodes(
     net: networkx.MultiGraph | networkx.MultiDiGraph,
     node_list: list[int | str],
     with_direction_flag: bool = False,
-    length_field: str = LENGTH_FIELD,
+    length_field: str | None = LENGTH_FIELD,
     return_unique: bool = True,
     shortest_path_only: bool = True,
 ) -> list[Edge]:
@@ -427,7 +427,7 @@ def get_edges_from_nodes(
         return edge_list
 
 
-def get_shortest_edge(edges: dict, length_field=LENGTH_FIELD):
+def get_shortest_edge(edges: dict, length_field: str | None = LENGTH_FIELD):
     """
     From a dictionary of edges, get the shortest edge
     by its length
@@ -438,10 +438,14 @@ def get_shortest_edge(edges: dict, length_field=LENGTH_FIELD):
     if not edges:
         raise ValueError("The edge list is empty")
 
-    min_key = min(
-        edges, key=lambda k: edges[k][length_field]
-    )  # py3 can add default=None
-    return min_key, edges[min_key]
+    if length_field is None:
+        # simply return the first edge
+        return next(iter(edges)), edges[next(iter(edges))]
+    else:
+        min_key = min(
+            edges, key=lambda k: edges[k][length_field]
+        )  # py3 can add default=None
+        return min_key, edges[min_key]
 
 
 def add_direction_flag(start_node, end_node, attributes, **kwargs):

wayfarer/routing.py

@@ -18,10 +18,12 @@ def solve_shortest_path(
     start_node: str | int,
     end_node: str | int,
     with_direction_flag: bool = True,
-    weight: str = LENGTH_FIELD,
+    weight: str | None = LENGTH_FIELD,
 ):
     """
-    Solve the shortest path between two nodes, returning a list of Edge objects
+    Solve the shortest path between two nodes, returning a list of Edge objects.
+    Set weight to the attribute name for deciding the shortest path, or to None
+    to ignore any weightings (faster).
     """
     nodes = solve_shortest_path_from_nodes(net, [start_node, end_node], weight)
     return functions.get_edges_from_nodes(
@@ -32,16 +34,16 @@ def solve_shortest_path(
 def solve_shortest_path_from_nodes(
     net: networkx.MultiGraph | networkx.MultiDiGraph,
     node_list: list[int | str],
-    weight: str = LENGTH_FIELD,
+    weight: str | None = LENGTH_FIELD,
 ) -> list[int | str]:
     """
     Return a list of nodes found by solving from each node in node_list to
-    the next
+    the next. Set weight to the attribute name for deciding the shortest path, or to None
+    to ignore any weightings (faster).
     """
     nodes_in_path = []
 
     for start_node, end_node in functions.pairwise(node_list):
-
         log.debug("Solving from %s to %s", start_node, end_node)
 
         if start_node == end_node:
@@ -361,8 +363,9 @@ def solve_all_shortest_paths(
     >>> pths = solve_all_shortest_paths(net, 0, 2)
     >>> print(list(pths))
     [[0, 1, 2]]
-    """
+
     # noqa: E501
+    """
 
     all_shortest_paths = []