added comments

Author: juanfonsecaLS1

superblockify/utils.py

@@ -88,43 +88,57 @@ def preprocess_graph(G: MultiDiGraph, boundary_buffer_dist: float = 200) -> Mult
     networkx.MultiDiGraph
         The preprocessed graph.
     """
-        
+
+    # Add edge bearings    
     G = ox.add_edge_bearings(G)    
 
+    # Checks if the graph is projected, if not it projects it to the local UTM.
     if not ox.projection.is_projected(G.graph["crs"]):
         G = ox.project_graph(G)
-        
+    
+    # A geodataframe is created from the projected graph for extracting the
+    # boundary of the graph. And, if missing, extract the lenghts of the geometies 
     edges_gdf = ox.graph_to_gdfs(G, nodes=False, edges=True)
     names_attribute = edges_gdf.columns
 
+    # Checks if the lenght is missing, e.g. the graph was not created with osmnx, and adds it if necessary
     if "length" not in names_attribute:
         logger.warning(
             "Length attribute is not present in the graph. Calculating lengths from geometry."
         )
         edges_lengths = edges_gdf.geometry.length
         set_edge_attributes(G, edges_lengths.to_dict(), name="length")
 
+    # Checks if the maxspeed attribute is missing, e.g. this is not a graph from OSM data.
+    # Adds a default maxspeed of 30 km/h if it is missing, as this is needed for calculating
+    # travel times. 
     if "maxspeed" not in names_attribute:
         logger.warning(
-            "maxspeed attribute is not present in the graph. Global max speeds are going to be set to 30."
+            "maxspeed attribute is not present in the graph. Global max speeds are going to be set to 30 km/h."
         )
         set_edge_attributes(G, 30, name="maxspeed")
 
+    # Add speeds and travel times using  osmnx 
     G = ox.add_edge_speeds(G)
     G = ox.add_edge_travel_times(G)
 
 
+    # Create a convex hull of the graph to calculate the area and set the boundary for saving the graph.
+    # This is implemented with an if statement to support older versions of geopandas < 1.0.0 
     if hasattr(edges_gdf.geometry, "unary_union"):
         edge_union = edges_gdf.geometry.unary_union
     else:
         edge_union = edges_gdf.geometry.union_all()
 
+    # A convex hull is created arround the bufferred edges.
     enclosing_hull = edge_union.buffer(boundary_buffer_dist).convex_hull
 
+    # Assigning the attributes to the graph
     G.graph.update(basic_graph_stats(G, area=enclosing_hull.area))
     G.graph["area"] = enclosing_hull.area
     G.graph['boundary'] = enclosing_hull
 
+    # Adding the edge population data
     add_edge_population(G)
 
     return G