Iterating over (selected) features by the same id

Question

I have a feature class Test_NearestNeighbor_Code. This feature class has 7373 polygon features and a column/ field called osm_id. I want to do a calculation with all features that have the same osm_id. How can I do this in arcpy in an iterative way over all features (without using the ModelBuilder)?

Calculate Field code works, but loop with SearchCursor doesn't, any suggestions for improvement?

Attached the Attribute Table of the feature class Test_NearestNeigbour_Code.

with arcpy.da.SearchCursor("Test_NearestNeighbour_Code", ["osm_id"]) as cursor:
    for row in cursor:
        arcpy.management.CalculateField("Test_NearestNeighbour_Code", "Dispersitätsmaß", "nn_output[1]", "PYTHON3", 'nn_output = arcpy.stats.AverageNearestNeighbor("Test_NearestNeighbour_Code", "EUCLIDEAN_DISTANCE", "NO_REPORT", None)', "DOUBLE", "NO_ENFORCE_DOMAINS")```

Answer 1

Providing your features have unique id field called "UNIQ_ID" and osm_id is integer field the script below should work.

INPUT:

Script:

import arcpy
inLayer = "all_points"
aSet = set(row[0] for row in arcpy.da.TableToNumPyArray(inLayer,"OSM_ID"))
tempFc = "in_memory/selected"
aDict={}
for item in aSet:
    arcpy.AddMessage('Processing item %s' %item)
    arcpy.analysis.Select(inLayer, tempFc, '"osm_id" =%i'%item) #modify query if osm_id is a string
    result = arcpy.stats.AverageNearestNeighbor(tempFc)[1]
    tbl=arcpy.da.TableToNumPyArray(tempFc,"UNIQ_ID")
    for row in tbl:aDict[row[0]]=result #memorize result in dictionary
arcpy.AddMessage('Results transfer...')
with arcpy.da.UpdateCursor(inLayer,("UNIQ_ID","z_score")) as cursor:
    for oid,z in cursor:cursor.updateRow((oid,aDict[oid]))

OUTPUT:

Answer 2

with > 1, it works with "cursor.updateRow((oid,aDict[oid]))", but with a result in the column "Dispersitätsmaß" of features, which getCount <=1 . For them, it should be no result (), because the calculation should not be carried out. Any suggestions to improve this?

with "cursor.updateRow((oid,aDict.get([oid],-1)))" below, i´ll get this error message

import numpy
inLayer = "Test_NearestNeighbour_Code"
aSet = set(row[0] for row in arcpy.da.TableToNumPyArray(inLayer,"osm_id_zahl_double"))
tempFc = "selected"
aDict={}
for item in aSet:
    arcpy.AddMessage('Processing item %s' %item)
    arcpy.analysis.Select(inLayer, tempFc, '"osm_id_zahl_double" =%i'%item) 
    if int(arcpy.GetCount_management(tempFc).getOutput(0)) > 1 :
        result = arcpy.stats.AverageNearestNeighbor(tempFc)[1]
    tbl=arcpy.da.TableToNumPyArray(tempFc,"osm_id_zahl_double")
    for row in tbl:aDict[row[0]]=result
arcpy.AddMessage('Results transfer...')
with arcpy.da.UpdateCursor(inLayer,("osm_id_zahl_double","Dispersitätsmaß")) as cursor:
    for oid,z in cursor:cursor.updateRow((oid,aDict.get([oid],-1)))

TypeError                                 Traceback (most recent call last)
In  [7]:
Line 15:    for oid,z in cursor:cursor.updateRow((oid,aDict.get([oid],-1)))

TypeError: unhashable type: 'list'