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Reference

Road network loading functions​

Dash Sylvereye provides helpers for loading and visualizing OpenStreetMap (OSM) road-network data produced by the OSMnx library.

The loading functions documented below live in the dash_sylvereye.utils module.

load_from_osmnx_graph​

load_from_osmnx_graph converts a NetworkX graph returned by OSMnx's graph_from_place into the nodes_data and edges_data lists consumed by Dash Sylvereye.

For each node, load_from_osmnx_graph copies the following OSM fields (when present) into the node's data key:

  • osmid (OSM ID)
  • highway
  • x (longitude)
  • y (latitude)

Example contents of a node's data key:

{'highway': None,
 'osmid': 3015359332,
 'x': -100.4082449,
 'y': 20.5537155}

For each edge, load_from_osmnx_graph copies the following OSM fields (when present) into the edge's data key:

Example contents of an edge's data key:

{'access': None,
 'bridge': None,
 'geometry': 'LINESTRING (-100.3859634 20.5416189,  '
            '-100.3857662 20.5422811, -100.3856528  '
             '20.5432228, -100.38552 20.5441006,    '
             '-100.3854999 20.5444598, -100.3854269 '
             '20.5447641, -100.3851515 20.5451256)  ',
 'highway': 'unclassified',
 'id': None,
 'junction': None,
 'lanes': None,
 'length': '404.454',
 'maxspeed': None,
 'name': None,
 'oneway': 'False',
 'osmid': 351963225,
 'ref': None,
 'service': None,
 'source_osmid': '3577605387',
 'target_osmid': '3577605678'}

The following example fetches the road-network topology of Querétaro through OSMnx and visualizes the result with SylvereyeRoadNetwork:

import osmnx as ox
from dash_html_components import Div
from dash_sylvereye import SylvereyeRoadNetwork
from dash_sylvereye.utils import load_from_osmnx_graph

OSMNX_QUERY = "Santiago de Queretaro, Queretaro, Mexico"

# retrieve road network topology and data from OSM
road_network = ox.graph_from_place(OSMNX_QUERY, network_type='drive') 
nodes_data, edges_data = load_from_osmnx_graph(road_network)

# dashboard setup
# 'app' is the app Dash object
app.layout = Div([
    SylvereyeRoadNetwork(
                         ...
                         nodes_data=nodes_data,
                         edges_data=edges_data
                         ...
                        )
                         
])

The following example pretty-prints the OSM data attached to the Dash Sylvereye nodes and edges:

import pprint
import osmnx as ox
from dash_html_components import Div
from dash_sylvereye import SylvereyeRoadNetwork
from dash_sylvereye.utils import load_from_osmnx_graph

OSMNX_QUERY = "Santiago de Queretaro, Queretaro, Mexico"

# retrieve the road network topology and data from OSM
road_network = ox.graph_from_place(OSMNX_QUERY, network_type='drive') 
nodes_data, edges_data = load_from_osmnx_graph(road_network)

# print the data in nodes
for node in nodes_data:
    print(f"Node {node['osmid']}:")
    pprint.pprint(node['data'])

# print the data in edges
for edge in edges_data:
    print(f"Edge {edge['data']['source_osmid']} -> {edge['data']['target_osmid']}:")
    pprint.pprint(edge['data'])

Parameters​

Name: g
Type: NetworkX graph

NetworkX graph returned by the graph_from_place function of the OSMnx library.

Returns​

The function returns 2 values:

Type: list of dict

List of Dash Sylvereye nodes.

Type: list of dict

List of Dash Sylvereye edges.

load_from_osmnx_graphml​

load_from_osmnx_graphml reads a GraphML file produced by OSMnx's save_graphml and returns the Dash Sylvereye nodes_data and edges_data lists, plus the underlying NetworkX graph.

For each node, load_from_osmnx_graphml copies the following OSM fields (when present) into the node's data key:

  • osmid (OSM ID)
  • highway
  • x (longitude)
  • y (latitude)

Example contents of a node's data key:

{'highway': None,
 'osmid': 3015359332,
 'x': -100.4082449,
 'y': 20.5537155}

For each edge, load_from_osmnx_graphml copies the following OSM fields (when present) into the edge's data key:

Example contents of an edge's data key:

{'access': None,
 'bridge': None,
 'geometry': 'LINESTRING (-100.3859634 20.5416189,  '
            '-100.3857662 20.5422811, -100.3856528  '
             '20.5432228, -100.38552 20.5441006,    '
             '-100.3854999 20.5444598, -100.3854269 '
             '20.5447641, -100.3851515 20.5451256)  ',
 'highway': 'unclassified',
 'id': None,
 'junction': None,
 'lanes': None,
 'length': '404.454',
 'maxspeed': None,
 'name': None,
 'oneway': 'False',
 'osmid': 351963225,
 'ref': None,
 'service': None,
 'source_osmid': '3577605387',
 'target_osmid': '3577605678'}

The following example loads a road network from Queretaro.graphml and visualizes it with SylvereyeRoadNetwork:

import osmnx as ox
from dash_html_components import Div
from dash_sylvereye import SylvereyeRoadNetwork
from dash_sylvereye.utils import load_from_osmnx_graphml

GRAPHML_FILEN = "data/Queretaro.graphml"

# load road network topology and data from disk
nodes_data, edges_data, g = load_from_osmnx_graphml(GRAPHML_FILEN)

# print number of nodes and edges from the loaded NetworkX graph
print(f'Nodes: {g.number_of_nodes()} / Edges: {g.number_of_edges()}')

# dashboard setup
# 'app' is the app Dash object
app.layout = Div([
    SylvereyeRoadNetwork(
                         ...
                         nodes_data=nodes_data,
                         edges_data=edges_data
                         ...
                        )
                         
])

The following example pretty-prints the OSM data attached to the Dash Sylvereye nodes and edges loaded from disk:

import pprint
import osmnx as ox
from dash_html_components import Div
from dash_sylvereye import SylvereyeRoadNetwork
from dash_sylvereye.utils import load_from_osmnx_graphml

GRAPHML_FILEN = "data/Queretaro.graphml"

# load road network topology and data from disk
nodes_data, edges_data, g = load_from_osmnx_graphml(GRAPHML_FILEN)

# print number of nodes and edges from the loaded NetworkX graph
print(f'Nodes: {g.number_of_nodes()} / Edges: {g.number_of_edges()}')

# print the data in nodes
for node in nodes_data:
    print(f"Node {node['osmid']}:")
    pprint.pprint(node['data'])

# print the data in edges
for edge in edges_data:
    print(f"Edge {edge['data']['source_osmid']} -> {edge['data']['target_osmid']}:")
    pprint.pprint(edge['data'])

Parameters​

Name: filen
Type: str

File name of the GraphML file generated by the save_graphml function of the OSMnx library.

Returns​

The function returns 3 values:

Type: list of dict

List of Dash Sylvereye nodes.

Type: list of dict

List of Dash Sylvereye edges.

Type: NetworkX graph

NetworkX graph of the loaded road network.

load_from_sumo_network​

load_from_sumo_network builds a Dash Sylvereye road network from a SUMO .net.xml network file. It returns the same (nodes_data, edges_data, g) triple as load_from_osmnx_graphml, where g is the underlying SUMO sumolib.net.Net object.

It can be imported from the dash_sylvereye.utils module.

caution

This function requires the SUMO traffic simulator's Python bindings (sumolib). They are not installed with the base dash-sylvereye package. Either:

  • Install the optional extra: pip install dash-sylvereye[sumolib] (pulls sumolib from PyPI).
  • Or install SUMO system-wide (apt install sumo on Debian/Ubuntu) and leave the default sumolib_path so the system package is found on sys.path.

Without one of those, calling load_from_sumo_network raises ModuleNotFoundError: No module named 'sumolib'.

The following example loads a SUMO network from disk and visualizes it with SylvereyeRoadNetwork:

from dash_html_components import Div
from dash_sylvereye import SylvereyeRoadNetwork
from dash_sylvereye.utils import load_from_sumo_network

SUMO_NET_FILEN = "data/queretaro.net.xml"

# load road network topology from a SUMO net.xml file
nodes_data, edges_data, g = load_from_sumo_network(SUMO_NET_FILEN)

# 'app' is the app Dash object
app.layout = Div([
    SylvereyeRoadNetwork(
                         ...
                         nodes_data=nodes_data,
                         edges_data=edges_data,
                         ...
                        )
])

Each node's data dict carries: id, type, lat, lon. Each edge's data dict carries: id, from_node_id, to_node_id, length, name, priority, is_special, speed, function, lane_number, and a lanes sub-list with per-lane id, length, speed, width, and coords.

Parameters​

Name: filen
Type: str

File name of the SUMO .net.xml network file.

Name: sumolib_path
Type: str
Default: "/usr/share/sumo/tools"

Filesystem path to the SUMO sumolib library, usually the tools/ directory of the SUMO install. Ignored when sumolib is already importable (e.g. installed via the sumolib extra).

Returns​

The function returns 3 values:

Type: list of dict

List of Dash Sylvereye nodes.

Type: list of dict

List of Dash Sylvereye edges.

Type: sumolib.net.Net

The SUMO road network object.