def update_parcel_geometry(SWU_Parcels, Update_Parcels):

    #create parcel geometry dictionaries d1, d2
    cursor_fields = ['PID','SHAPE@','OID@']
    #dicts have index 0 as key and tuple of remainder as value
    arcpy.AddMessage('Reading SWU parcel geometries ...')
    with arcpy.da.SearchCursor(SWU_Parcels,cursor_fields) as cursor:
        d1 = {tup[0]:tup[1:] for tup in cursor}
    arcpy.AddMessage('Reading Update parcel geometries ...')
    with arcpy.da.SearchCursor(Update_Parcels,cursor_fields) as cursor:
        d2 = {tup[0]:tup[1:] for tup in cursor}

    #create dict of updated geoemetries
        # format { PID : SHAPE }
    update_dict = {t[0]: t[1][0] for t in d2.items() if t[0] in d1 and t[1][0] != d1[t[0]][0]}

    #create update cursor
    upd_fields = ['PID','SHAPE@','LAST_MODIFIED_BY','LAST_MODIFIED_DATE']
    with arcpy.da.UpdateCursor(SWU_Parcels,upd_fields) as upd_cursor:
        #commit updates
        for row in upd_cursor:
            if row[0] in update_dict:
                last_modified_by = 'ParcelScript'
                last_modified_date = datetime.datetime.now()
                PID = row[0]
                SHAPE = update_dict[row[0]]
                try:
                    update = (PID,SHAPE,last_modified_by,last_modified_date)
                    upd_cursor.updateRow(update)
                    arcpy.AddMessage('Updating geometry for PID {}'.format(row[0]))
                except Exception as e:
                    arcpy.AddMessage(e.args[0])