Arcpy error: updating attribute values in relationship class table

Question

I'm attempting to update the attribute values in a relationship class table using python. basically, i'm looking to update two count fields to see how many times each primary key occurs in the table, and then set a 'matchType', ie is it '1 to 1', '1 to many', etc... here is my code: import arcpy arcpy.env.workspace = 'C:\Users\Werfel\Desktop\Philly PIN\matches.gdb' dor = {} pwd = {} with arcpy.da.SearchCursor('dor_pwd',['DOR_OBJECTID','PARCELID']) as cursor: for row in cursor: if row[0] not in dor.keys(): dor[row[0]] = 1 else: dor[row[0]] += 1 if row[1] not in pwd.keys(): pwd[row[1]] = 1 else: pwd[row[1]] += 1 #edit = arcpy.da.Editor(arcpy.env.workspace) #edit.startEditing(False, False) #edit.startOperation() with arcpy.da.UpdateCursor('dor_pwd',['DOR_OBJECTID','PARCELID','dorCount','pwdCount','matchType']) as cursor: for row in cursor: row[2] = dor[row[0]] row[3] = pwd[row[1]] if dor[row[0]]==1 and pwd[row[1]]==1: row[4]='1-1' if dor[row[0]]==1 and pwd[row[1]]>1: row[4]='M-1' if dor[row[0]]>1 and pwd[row[1]]==1: row[4]='1-M' if dor[row[0]]>1 and pwd[row[1]]>1: row[4]='M-M' cursor.updateRow(row) #edit.stopOperation() #edit.stopEditing(True) ‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍ it crashes on line 32, with the message: RuntimeError: Cannot reset foreign key values for an existing relationship row thing is, none of the rows i'm updating are foreign keys. row[0] and row[1] are, but i'm only reading them. is it bc the UpdateCursor retrieves these fields? i can think of other ways to do this (summary table, for example), but this is by far the fastest that i came up with, and i would like to run this every time i create a relationship, of which there will be thousands fyi, the commented lines are to indicate that i have i tried with and without an edit session any ideas?? thanks in advance,

dougbrowning · Answer

You could not use a Update Cursor.

What I like to do is

Copy to in_memory
           arcpy.TableToTable_conversion(inDir + "\" + inDB + "\" + table, "in_memory", table)

Add a field

Calc the new field

Join back to original FC or table

Calc over the value

Now if it is a web map then you could just use Arcade and it would be love time dynamic.

Hope that helps.

ValCannon2 · Answer

I'm getting the same error in ArcGIS Pro but if I close the application and run the script in PyCharm (or IDLE, I assume) it runs great. This looks like a bug with a workaround for me.