Item not found in this collection error - UpdateCursor on Query Table

Question

The following code:

with arcpy.da.UpdateCursor("QueryTable", ("SHAPE", "leakage_with_pon_list_Eastings", "leakage_with_pon_list_Northings", "leakage_with_pon_list_RandomNumber")) as cursor:
  for row in cursor:
  row[1] = row[0].positionAlongLine(row[3], True).X
  row[2] = row[0].positionAlongLine(row[3], True).Y

cursor.updateRow(row)

fails with an "item not found in this collection" error, apparently on line 02. Is it not possible to use an update cursor on a query table or something?

JamesCrandall · Answer

I struggle with this type of stuff because python is so finicky with specifics and I never know what I can get away with

JoshuaBixby · Answer

You mention "query table."  Are you using Make Query Table or Make Query Layer?  Make Query Table is powerful, but it is an older tool, and I am not sure if its outputs are editable.

I just did a quick test using Make Query Table where I took a single feature class and used Make Query Table to create a layer, so this is a very simple case without multiple data sets or joins.  Although I could use an update cursor on the feature class directly, I could not use it on the layer created from Make Query Table.

JoshuaBixby · Answer

Although using lists for field names is much more common, tuples are supported.  I am leaning more towards the query table.