Refering to (Joined) Field Names in arcpy in Field Calculator

Question

I'm trying to update the locations of a point FeatureClass using a table.

I have joined the table to the featureclass, and am attempting to use Field Calculator to update the SHAPE field.

I found the following code snippet that does what I want:

def Update(shape, newX, newY):
   pnt = shape.getPart(0)
   pnt.X = newX
   pnt.Y = newY
   return pnt

Update( !SHAPE! , !NEAR_X! , !NEAR_Y! )

which ends up looking like this:

When I try this on a test featureclass, with no joined fields (just 3 columns; shape, newX, newY) it works perfectly. However, when I try it on my real data, with the table joined, it will not work. It gives a 'Failed to execute' error, and the ever-joyful 'ERROR 999999: Error executing function.'

I have tried making a Feature Layer from the joined table, and that doesn't help either.

How do I properly refer to the field names to make this work?

EDIT: In response to @Emil Brundage - when running the query on the joined layer, I did use the tablename.fieldname structure, as per the image below.

I receive a syntax error:

Answer 1

Once a table is joined you need the name of the table where the field originated as well as the field name, separated by a period.

Update ( !test2.Shape!, !test1.NEAR_X!, !test1.NEAR_Y!)

Answer 2

There is nothing wrong with your syntax, even though ArcMap would like you to think so. Use similar syntax on any other field and it will work.

The issue is that the SHAPE field is read only for Field Calculator when the table has a join. A solution would be to remove any joins, and then join the NEAR_X and NEAR_Y fields using Join Field, and then use Field Calculator with the following code:

arcpy.PointGeometry( arcpy.Point( !NEAR_X!, !NEAR_Y! ) )

You could also use an UpdateCursor and SearchCursor to do what you want without the need for joins or copying fields, but that is for another question.