Minor Cleanup to Chapter 4 to make the book more readable

Author: davecom

Chapter4/dijkstra.py

@@ -57,16 +57,16 @@ def dijkstra(wg: WeightedGraph[V], root: V) -> Tuple[List[Optional[float]], Dict
     return distances, path_dict
 
 
-# helper function to get easier access to dijkstra results
+# Helper function to get easier access to dijkstra results
 def distance_array_to_vertex_dict(wg: WeightedGraph[V], distances: List[Optional[float]]) -> Dict[V, Optional[float]]:
     distance_dict: Dict[V, Optional[float]] = {}
     for i in range(len(distances)):
         distance_dict[wg.vertex_at(i)] = distances[i]
     return distance_dict
 
 
-# Takes a dictionary of edges to reach each node and returns an array of edges
-# that goes from `start` to `end`
+# Takes a dictionary of edges to reach each node and returns a list of
+# edges that goes from `start` to `end`
 def path_dict_to_path(start: int, end: int, path_dict: Dict[int, WeightedEdge]) -> WeightedPath:
     if len(path_dict) == 0:
         return []
@@ -111,8 +111,11 @@ def path_dict_to_path(start: int, end: int, path_dict: Dict[int, WeightedEdge])
 
     distances, path_dict = dijkstra(city_graph2, "Los Angeles")
     name_distance: Dict[str, Optional[int]] = distance_array_to_vertex_dict(city_graph2, distances)
+    print("Distances from Los Angeles:")
     for key, value in name_distance.items():
         print(f"{key} : {value}")
+    print("") # blank line
 
+    print("Shortest path from Los Angeles to Boston:")
     path: WeightedPath = path_dict_to_path(city_graph2.index_of("Los Angeles"), city_graph2.index_of("Boston"), path_dict)
     print_weighted_path(city_graph2, path)

Chapter4/mst.py

@@ -22,6 +22,10 @@
 WeightedPath = List[WeightedEdge] # type alias for paths
 
 
+def total_weight(wp: WeightedPath) -> float:
+    return sum([e.weight for e in wp])
+
+
 def mst(wg: WeightedGraph[V], start: int = 0) -> Optional[WeightedPath]:
     if start > (wg.vertex_count - 1) or start < 0:
         return None
@@ -47,10 +51,6 @@ def visit(index: int):
     return result
 
 
-def total_weight(wp: WeightedPath) -> float:
-    return sum([e.weight for e in wp])
-
-
 def print_weighted_path(wg: WeightedGraph, wp: WeightedPath) -> None:
     for edge in wp:
         print(f"{wg.vertex_at(edge.u)} {edge.weight}> {wg.vertex_at(edge.v)}")