ArcPy updating fields from another table

Question

I'm trying to update missing values in one .shp from another .shp. I'm using SelectLayerByLocation to identify the properties which lie within the boundaries of a suburb and then using a UpdateCursor to update the properties list with the suburbs. The code below doesn't iterate through the list correctly so all I get is the first value from the initial SearchCursor updating the properties list.

fc_P = propertyDataset
fc_S = suburbsDataset
LOCALITYList = []
query = '"LOCALITY" =\'\''
field_P = ["LOCALITY"]
field_S = ["ADMINAREA"]
arcpy.MakeFeatureLayer_management(fc_S,"Suburbs_layer")
arcpy.MakeFeatureLayer_management(fc_P,"Properties_layer", query)
arcpy.SelectLayerByLocation_management("Properties_Layer", "WITHIN", 
"Suburbs_Layer")
with arcpy.da.SearchCursor("Suburbs_layer",field_S) as Srow:
 for row in Srow:
 Suburb = Srow[0]
with arcpy.da.UpdateCursor("Properties_layer", field_P) as Ucursor:
 for Urow in Ucursor:
 Urow[0] = Suburb
 Ucursor.updateRow(Urow)
del Ucursor
del Srow

suburbs.shp attribute table properties.shp attribute table

• Bera: You are not iterating over localitylist in the code you present (for locality in localitylist:)
• Brett: i was using the localitylist to get a count of properties updated later in the code. would it be best to append the list during the search cursor and then use that within the update cursor?
• Bera: Are you trying to update properties that does not have a suburb (ADMINAREA?)? A screenshot showing the attribute tables and maybe the map would help in understanding your question.
• Brett: thats exactly what i'm trying to do. the locality in the properties dataset is named adminarea in the suburbs dataset. some properties dont have localities/adminareas listed.
• Brett: when i run the code it grabs the result from the row 0 in the property .shp which is toowoomba city and uses that that to fill in the blanks.

Answer 1

I think you should try using spatial join instead. That way you dont need to iterate Select Layer By Location and multiple cursors. The output can be written to in_memory so that it not saved to disk and the output is used to create a dictionary of objectids and their suburb.

Try code below, I have no data to try it on so you might get some errors:

import arcpy
propfc = 'Properties'
subfc = 'Suburbs'
propfc_suburbfield = 'LOCALITY'
subfc_suburbfield = 'ADMINAREA'
#Create feature layer of properties with LOCALITY shorter than 2 charachters
sql = "CHAR_LENGTH({0})<2".format(arcpy.AddFieldDelimiters(propfc, propfc_suburbfield))
arcpy.MakeFeatureLayer_management(in_features=propfc, out_layer='proplyr', where_clause=sql)
#Spatial join suburbs to properties layer
tempspatjoin = r'in_memory\spatjoin'
arcpy.SpatialJoin_analysis(target_features='proplyr', join_features=subfc, out_feature_class=tempspatjoin, join_type='KEEP_COMMON',\
 match_option='WITHIN')
#Create a dictionary of property objectids and what suburb they are in
updatedictionary = {k:v for k,v in arcpy.da.SearchCursor(tempspatjoin,['TARGET_FID',subfc_suburbfield])}
#Update proplyr with suburbs from dictionary
with arcpy.da.UpdateCursor('proplyr',['OID@',propfc_suburbfield]) as cursor:
 for row in cursor:
 if row[0] in updatedictionary: #If this rows oid is in dictionary
 row[1] = updatedictionary[row[0]] #Update with suburb
 cursor.updateRow(row)