# Name: MakeServiceAreaAnalysisLayer_Workflow2.py
# Description: Generate 3-minute service areas around fire stations at several
# times of day to compare coverage differences due to varying
# traffic conditions. Save the results to a feature class on disk.
# Requirements: Network Analyst Extension
# Import system modules
import arcpy
from arcpy import env
import os, datetime
try:
# Check out Network Analyst license if available. Fail if the Network Analyst license is not available.
if arcpy.CheckExtension("network") == "Available":
arcpy.CheckOutExtension("network")
else:
raise arcpy.ExecuteError("Network Analyst Extension license is not available.")
# Set environment settings
output_dir = "C:/Data"
# The NA layer's data will be saved to the workspace specified here
env.workspace = os.path.join(output_dir, "Output.gdb")
env.overwriteOutput = True
# Set local variables
input_gdb = "C:/Data/SanFrancisco.gdb"
network = os.path.join(input_gdb, "Transportation", "Streets_ND")
layer_name = "FireStationCoverage"
out_featureclass = os.path.join(output_dir, "Output.gdb",
"FireStationCoverage")
travel_mode = "Driving Time"
facilities = os.path.join(input_gdb, "Analysis", "FireStations")
times_of_day = [datetime.datetime(2014, 9, 25, 7, 0, 0),
datetime.datetime(2014, 9, 25, 12, 30, 0),
datetime.datetime(2014, 9, 25, 17, 30, 0),
datetime.datetime(2014, 9, 25, 21, 0, 0)]
# Create a new service area layer.
result_object = arcpy.na.MakeServiceAreaAnalysisLayer(network, layer_name,
travel_mode, "FROM_FACILITIES",
[3], polygon_detail="HIGH",
geometry_at_overlaps="OVERLAP")
# Get the layer object from the result object. The service area layer can
# now be referenced using the layer object.
layer_object = result_object.getOutput(0)
# Get the names of all the sublayers within the service area layer.
sublayer_names = arcpy.na.GetNAClassNames(layer_object)
# Stores the layer names that we will use later
facilities_layer_name = sublayer_names["Facilities"]
polygons_layer_name = sublayer_names["SAPolygons"]
# The input data has a field for FireStationID that we want to transfer to
# our analysis layer. Add the field, and then use field mapping to transfer
# the values.
arcpy.na.AddFieldToAnalysisLayer(layer_object, facilities_layer_name,
"FireStationID", "TEXT")
field_mappings = arcpy.na.NAClassFieldMappings(layer_object,
facilities_layer_name)
field_mappings["FireStationID"].mappedFieldName = "FireStationID"
# Load the fire stations as facilities.
arcpy.na.AddLocations(layer_object, facilities_layer_name, facilities,
field_mappings, "")
# Add fields to the output Polygons sublayer for later use.
arcpy.na.AddFieldToAnalysisLayer(layer_object, polygons_layer_name,
"FireStationID", "TEXT")
arcpy.na.AddFieldToAnalysisLayer(layer_object, polygons_layer_name,
"TimeOfDay", "TEXT")
# Get sublayers to work with later
facilities_sublayer = arcpy.na.GetNASublayer(layer_object, "Facilities")
polygons_sublayer = arcpy.na.GetNASublayer(layer_object, "SAPolygons")
# Get the Service Area Layer's solver properties. This can be used to
# set individual properties later without re-creating the layer.
solver_properties = arcpy.na.GetSolverProperties(layer_object)
# Solve the Service Area for each time of day in the time list
for t in times_of_day:
print("Calculating service area for time of day: ", t)
# Use the solver properties to set the time of day for the solve
solver_properties.timeOfDay = t
# Solve the service area layer
arcpy.na.Solve(layer_object)
# Transfer the FireStationID field from the input Facilities to the
# output Polygons
arcpy.management.AddJoin(polygons_sublayer, "FacilityID",
facilities_sublayer, "ObjectID")
# The joined fields are qualified by the feature class name of the joined
# table, so determine the feature class names
field_qualifier_pol = os.path.basename(polygons_sublayer.dataSource)
target_field_name = "%s.FireStationID" % field_qualifier_pol
field_qualifier_fac = os.path.basename(facilities_sublayer.dataSource)
expression = "!%s.FireStationID!" % field_qualifier_fac
arcpy.management.CalculateField(polygons_sublayer, target_field_name,
expression, "PYTHON")
arcpy.management.RemoveJoin(polygons_sublayer)
# Populate the TimeOfDay field in the output feature class
expression = '"' + str(t) + '"'
arcpy.management.CalculateField(polygons_sublayer, "TimeOfDay",
expression, "PYTHON")
# Append the polygons to the output feature class. If this was the first
# solve, create the feature class.
if not arcpy.Exists(out_featureclass):
arcpy.management.CopyFeatures(polygons_sublayer, out_featureclass)
else:
arcpy.management.Append(polygons_sublayer, out_featureclass)
print("Script completed successfully")
except Exception as e:
# If an error occurred, print line number and error message
import traceback, sys
tb = sys.exc_info()[2]
print("An error occurred on line %i" % tb.tb_lineno)
print(str(e))