Python crashing while processing cursor

Question

I have a fairly small script which is running a cursor on a small feature class (~2500 features) which is crashing python with a python.exe has stopped working message.

I have a cursor that loops over features, deletes any that don't meet a set criteria, looks up field value keys in a dictionary, and updates another field with the dictionary value. This works well. But if I add in a check to deleteRow() any records that have a Null or a value that doesn't start with the letter O.

arcpy.FeatureClassToFeatureClass_conversion(r"mydatabase.sde\mydatabase.dbo.SitePolygon", "in_memory", "xTempPolygon")

with arcpy.da.UpdateCursor(r'in_memory\xTempPolygon', ['RecID', 'LotID', 'Owner', 'Manager', 'Class']) as cursor:
    for row in cursor:
        if row[2] != 'CITY' or row[4][:4].upper() == 'ROAD' or row[3].upper() in ['WASTEWATER', 'STORMWATER', 'WATERSUPPLY']:
            cursor.deleteRow()
        elif row[0] in resultDict:
            row[1] = resultDict[row[0]]
            cursor.updateRow(row)

        #################################################
        # If I add this block, it crashes
        if row[1] is None or row[1][0].upper() != 'O':
            cursor.deleteRow()
        #################################################

The resultDict is a dictionary that comes from a SQL lookup that returns RecID and LotID. These are looked up in the cursor and populates the LotID on the feature based on its RecID.

If I leave out the final if block, it runs without issue. If I add it in it crashes. I need it there because I'm ending up with some records that have a NULL or a value that doesn't start with O in the LotID field. I need these records deleted.

I need the extra if to run after the update to allow for the update to run, as no records have any values in row[1] before the update - they are all NULL so they'd all be deleted.

What is causing this crash, and how do I avoid it?

Answer 1

Thanks to @Vince and @NateWanner for two suggestions that pointed me in the right direction.

As @Vince had commented, I was trying to access a row that had been deleted.

I created an else block and moved my elif (and turned it into if) and the failing if block into the else so that it would only process on rows that hadn't yet been deleted.

arcpy.FeatureClassToFeatureClass_conversion(r"mydatabase.sde\mydatabase.dbo.SitePolygon", "in_memory", "xTempPolygon")

with arcpy.da.UpdateCursor(r'in_memory\xTempPolygon', ['RecID', 'LotID', 'Owner', 'Manager', 'Class']) as cursor:
    for row in cursor:
        if row[2] != 'CITY' or row[4][:4].upper() == 'ROAD' or row[3].upper() in ['WASTEWATER', 'STORMWATER', 'WATERSUPPLY']:
            cursor.deleteRow()
        else:
            if row[0] in resultDict:
                row[1] = resultDict[row[0]]
                cursor.updateRow(row)
            if row[1] is None or row[1][0].upper() != 'O':
                cursor.deleteRow()

This is now working as desired, although thinking on the two comments further leads me to believe there may be even better ways to construct this cursor that'll I'll investigate.