Update layer based on another layer

Question

I need to update the PrivateRoads 'Owner' field based on what city the private road is in. I have the following but it take for ever but doesn't populate the correct city. I know I can do a spatial join but I don't want to create a separate layer.

import sys, os, arcpy
import arcpy

## Works in file geodatabase
arcpy.env.overwriteOutput = True
workspace = "C:/temp/temp.gdb"

PR = "PrivateRoads"
CityLimits = 'City_Limits'

arcpy.MakeFeatureLayer_management(PR, "polyLyr")
arcpy.MakeFeatureLayer_management(CityLimits, "CitLyr")

with arcpy.da.UpdateCursor(PR, ['SHAPE@', 'OID@', 'Owner']) as cursor:
    for row in cursor:
        arcpy.management.SelectLayerByLocation("polyLyr", "HAVE_THEIR_CENTER_IN", "CitLyr", "", "NEW_SELECTION")

with arcpy.da.SearchCursor("CitLyr", ['CITY']) as cCursor:
                for cRow in cCursor:
                    row[2] = cRow[0]
                    cursor.updateRow(row)

2Quiker · Answer

I was able to accomplish what I needed with the following.

PR = "PrivateRoads"
CityLimits = 'City_Limits'

arcpy.MakeFeatureLayer_management(PR, "polyLyr")
arcpy.MakeFeatureLayer_management(CityLimits, "CitLyr")

unique_strings = []
with arcpy.da.SearchCursor("CitLyr", 'CITY') as cursor:
    for row in cursor:
        unique_strings.append(row[0])
        #print (unique_strings)

for unique in unique_strings:
    arcpy.SelectLayerByAttribute_management("CitLyr", 'NEW_SELECTION', "CITY = '{}'".format(unique))
    arcpy.SelectLayerByLocation_management("polyLyr", 'HAVE_THEIR_CENTER_IN', "CitLyr", "", "NEW_SELECTION")
    with arcpy.da.UpdateCursor(PR, 'Owner') as cursor:
        for row in cursor:
            row[0] = unique
            cursor.updateRow(row)

2Quiker · Answer

I tried the following but the print only prints one of the cities and for some reason it's populates only a a few private roads that are not inside city limits. Some of these will not be in a city.

I honestly thought it would simple and  wouldn't' involve .keys or dicts.

import sys, os, arcpy

arcpy.env.overwriteOutput = True
workspace = "C:/temp/temp.gdb"

PR = "PrivateRoads"
CityLimits = 'City_Limits'

arcpy.MakeFeatureLayer_management(PR, "polyLyr")
arcpy.MakeFeatureLayer_management(CityLimits, "CitLyr")
arcpy.management.SelectLayerByLocation("polyLyr", "HAVE_THEIR_CENTER_IN", "CitLyr", "", "NEW_SELECTION")

pr_oid_to_city_name = dict()

# Add code here to use a search cursor to scan the polyLyr and 
# populate the dict that maps the pr OID to the city name
with arcpy.da.SearchCursor("CitLyr", ['OID@', 'CITY']) as search_cursor:
    for oid, city_name in search_cursor:
        pr_oid_to_city_name[oid] = city_name

print(pr_oid_to_city_name[oid])
# Start an edit session. Must provide the workspace.
edit = arcpy.da.Editor(workspace)

# Edit session is started without an undo/redo stack for versioned data
# (for the second argument, use False for unversioned data)
edit.startEditing(True)

# Start an edit operation
edit.startOperation()

fields = ['OID@', 'Owner']
with arcpy.da.UpdateCursor(PR, fields) as cursor:
    for row in cursor:
        oid = row[0]
        if oid in pr_oid_to_city_name:
            row[1] = pr_oid_to_city_name[oid]
            cursor.updateRow(row)

edit.stopOperation()
# Stop the edit session and save the changes
edit.stopEditing(True)

DonMorrison1 · Answer

I would try to restructure the  code roughly as follows:

import sys, os, arcpy
import arcpy

## Works in file geodatabase
arcpy.env.overwriteOutput = True
workspace = "C:/temp/temp.gdb"

PR = "PrivateRoads"
CityLimits = 'City_Limits'

arcpy.MakeFeatureLayer_management(PR, "polyLyr")
arcpy.MakeFeatureLayer_management(CityLimits, "CitLyr")
arcpy.management.SelectLayerByLocation("polyLyr", "HAVE_THEIR_CENTER_IN", "CitLyr", "", "NEW_SELECTION")

pr_oid_to_city_name = dict()

# Add code here to use a search cursor scan the polyLyr and 
# populate the dict that maps the pr oid to the city name

with arcpy.da.UpdateCursor(PR, ['OID@', 'Owner']) as cursor:
    for oid, owner in cursor:
        if oid in pr_oid_to_city_name.keys():
            cursor.updateRow([oid, pr_oid_to_city_name[oid])