Open In Colab

Saving a network to a file

Save a cityseer prepared networkx graph to a file.

To save a graph or to visualise it from QGIS, convert it to a GeoDataFrame and save it using geopandas.

First, let’s create a simple OSM graph from a bounding box, using the same approach as before.

from shapely import geometry

from cityseer.tools import io

poly_wgs = geometry.box(
    -0.14115725966109327,
    51.509220662095714,
    -0.12676440185383622,
    51.51820111033659,
)
G = io.osm_graph_from_poly(poly_wgs)
print(G)

INFO:cityseer.tools.graphs:Generating interpolated edge geometries.
WARNING:cityseer.tools.util:The to_crs_code parameter 4326 is not a projected CRS
INFO:cityseer.tools.io:Converting networkX graph to CRS code 32630.
WARNING:cityseer.tools.util:The to_crs_code parameter 4326 is not a projected CRS
INFO:cityseer.tools.io:Processing node x, y coordinates.
INFO:cityseer.tools.io:Processing edge geom coordinates, if present.
INFO:cityseer.tools.graphs:Removing filler nodes.
INFO:cityseer.tools.util:Creating edges STR tree.
INFO:cityseer.tools.graphs:Removing filler nodes.
INFO:cityseer.tools.graphs:Removing dangling nodes.
INFO:cityseer.tools.graphs:Removing filler nodes.
INFO:cityseer.tools.util:Creating edges STR tree.
INFO:cityseer.tools.graphs:Splitting opposing edges.
INFO:cityseer.tools.graphs:Squashing opposing nodes
INFO:cityseer.tools.graphs:Merging parallel edges within buffer of 25.
INFO:cityseer.tools.util:Creating edges STR tree.
INFO:cityseer.tools.graphs:Splitting opposing edges.
INFO:cityseer.tools.graphs:Squashing opposing nodes
INFO:cityseer.tools.graphs:Merging parallel edges within buffer of 25.
INFO:cityseer.tools.util:Creating edges STR tree.
INFO:cityseer.tools.graphs:Splitting opposing edges.
INFO:cityseer.tools.graphs:Squashing opposing nodes
INFO:cityseer.tools.graphs:Merging parallel edges within buffer of 25.
INFO:cityseer.tools.util:Creating edges STR tree.
INFO:cityseer.tools.graphs:Splitting opposing edges.
INFO:cityseer.tools.graphs:Squashing opposing nodes
INFO:cityseer.tools.graphs:Merging parallel edges within buffer of 25.
INFO:cityseer.tools.util:Creating nodes STR tree
INFO:cityseer.tools.graphs:Consolidating nodes.
INFO:cityseer.tools.graphs:Merging parallel edges within buffer of 25.
INFO:cityseer.tools.graphs:Removing filler nodes.
INFO:cityseer.tools.util:Creating nodes STR tree
INFO:cityseer.tools.graphs:Consolidating nodes.
INFO:cityseer.tools.graphs:Merging parallel edges within buffer of 25.
INFO:cityseer.tools.graphs:Removing filler nodes.
INFO:cityseer.tools.util:Creating nodes STR tree
INFO:cityseer.tools.graphs:Consolidating nodes.
INFO:cityseer.tools.graphs:Merging parallel edges within buffer of 25.
INFO:cityseer.tools.graphs:Removing filler nodes.
INFO:cityseer.tools.util:Creating nodes STR tree
INFO:cityseer.tools.graphs:Consolidating nodes.
INFO:cityseer.tools.graphs:Merging parallel edges within buffer of 25.
INFO:cityseer.tools.graphs:Removing filler nodes.
INFO:cityseer.tools.util:Creating nodes STR tree
INFO:cityseer.tools.util:Creating edges STR tree.
INFO:cityseer.tools.graphs:Snapping gapped endings.
INFO:cityseer.tools.util:Creating edges STR tree.
INFO:cityseer.tools.graphs:Splitting opposing edges.
INFO:cityseer.tools.graphs:Merging parallel edges within buffer of 25.
INFO:cityseer.tools.graphs:Removing dangling nodes.
INFO:cityseer.tools.graphs:Removing filler nodes.
INFO:cityseer.tools.util:Creating edges STR tree.
INFO:cityseer.tools.graphs:Splitting opposing edges.
INFO:cityseer.tools.graphs:Squashing opposing nodes
INFO:cityseer.tools.graphs:Merging parallel edges within buffer of 25.
INFO:cityseer.tools.util:Creating nodes STR tree
INFO:cityseer.tools.graphs:Consolidating nodes.
INFO:cityseer.tools.graphs:Merging parallel edges within buffer of 25.
INFO:cityseer.tools.util:Creating edges STR tree.
INFO:cityseer.tools.graphs:Splitting opposing edges.
INFO:cityseer.tools.graphs:Squashing opposing nodes
INFO:cityseer.tools.graphs:Merging parallel edges within buffer of 25.
INFO:cityseer.tools.util:Creating nodes STR tree
INFO:cityseer.tools.graphs:Consolidating nodes.
INFO:cityseer.tools.graphs:Merging parallel edges within buffer of 25.
INFO:cityseer.tools.graphs:Removing filler nodes.
INFO:cityseer.tools.graphs:Merging parallel edges within buffer of 50.
INFO:cityseer.tools.graphs:Ironing edges.
INFO:cityseer.tools.graphs:Merging parallel edges within buffer of 1.
INFO:cityseer.tools.graphs:Removing dangling nodes.
INFO:cityseer.tools.graphs:Removing filler nodes.

MultiGraph with 382 nodes and 587 edges

Use the geopandas_from_nx function to convert the networkx dataset into a geopandas LineString GeoDataFrame.

streets_gpd = io.geopandas_from_nx(G)
streets_gpd.head()

INFO:cityseer.tools.io:Preparing node and edge arrays from networkX graph.

	names	routes	highways	levels	is_tunnel	is_bridge	geom	start_nd_key	end_nd_key	edge_idx
0	[beak street]	[]	[unclassified]	[0]	False	False	LINESTRING (698573.946 5710658.889, 698597.952...	108070	25473512	0
1	[beak street]	[]	[unclassified]	[0]	False	False	LINESTRING (698573.946 5710658.889, 698556.667...	108070	25473371	0
2	[kingly court]	[]	[pedestrian, footway]	[0]	True	False	LINESTRING (698573.946 5710658.889, 698573.05 ...	108070	5568839679	0
3	[upper john street]	[]	[unclassified]	[0]	False	False	LINESTRING (698607.761 5710618.003, 698575.964...	108070	25473|26169±12909|95675	0
4	[great marlborough street]	[]	[tertiary]	[0]	False	False	LINESTRING (698482.48 5710892.514, 698538.717 ...	9791491	21665965	0

Since this is now a geopandas GeoDataFrame, you can use it accordingly.

streets_gpd.plot()

geopandas can now be used to save the file to disk, it can then be accessed and edited from an application such as QGIS.

streets_gpd.to_file(
    "temp/save_streets_demo.gpkg",
    driver="GPKG",
)

INFO:pyogrio._io:Created 587 records

Conclusion

This notebook demonstrated how to convert a cityseer-prepared networkx graph into a geopandas GeoDataFrame using geopandas_from_nx, and then save it to disk as a GeoPackage file. This workflow is useful for exporting networks for inspection in GIS applications such as QGIS or for sharing datasets with collaborators.

Next steps: For analysis, see Network Centrality or Accessibility.