Updating z values from joined table using ArcPy?

Question

I have joined two tables. The first table includes the current z values, while the new table includes new z values. I first tried to snap, but this didn't update the Z values, only X and Y. How can I update the z values of the joined table? I tried some python scripting, but Im not very good at it.

import arcpy
mast = "VoltTotal.GDB\Export_Output"
with arcpy.da.UpdateCursor(mast['test_endre_geom.SHAPE@Z','feat3d.POINT_Z']) as cursor:
 for row in cursor: 
 row[0] = row[1]
 cursor.updateRow(row)

Currently I'm getting an error displaying: RuntimeError: A column was specified that does not exist.

• jbchurchill: for starters the syntax does not look right on the UpdateCursor(fc, fields). The variable mast should be separated from the list of fields by a comma.
• birks: @jbchurchill Thats correct, well spottet, but I think that was only a copying error as the original code include the coma. I updated the post to reflect that.
• Hornbydd: Your field list appears to be using 2 fields from different tables as they have table names before the field name.. That is not how the cursor works, you can only process fields from the single featureclass, in your case mast.
• birks: @Hornbydd Thank you, that was what I was wondering about. Do you have any idea how I could approach this problem? I'm not very skilled in python.
• jbchurchill: If you have a field that matches in both tables you can run your update cursor within a search cursor so that when it finds a match, it updates the values in the other table.

Answer 1

Use cursors and make use of dictionaries to avoid nested loops.

import arcpy
mast = "VoltTotal.GDB\Export_Output"
shapeFile = "PathToMy\test_endre_geom.shp"
di = {}
with arcpy.da.SearchCursor(mast, ['M_FIELD', 'POINT_Z']) as cursor:
 for m, z in cursor:
 di [m] = z
with arcpy.da.UpdateCursor(shapeFile, ['M_FIELD', 'SHAPE@Z']) as cursor:
 for m, z in cursor:
 z = di [m]
 row = (m, z)
 cursor.updateRow (row)

Answer 2

To elaborate on my comment, I'm providing a potential solution. I'm assuming mast is the table and test_endre_geom.shp is the shapefile. The field 'M_FIELD' is a field that matches in both layers.

import arcpy
mast = "VoltTotal.GDB\Export_Output"
shapeFile = "PathToMy\test_endre_geom.shp"
with arcpy.da.SearchCursor(mast,['M_FIELD', 'POINT_Z']) as outsidecursor:
 for row in outsidecursor:
 matchValue = row[0]
 tableValue = row[1]
 with arcpy.da.UpdateCursor(shapeFile,['M_FIELD', 'SHAPE@Z']) as cursor:
 for row in cursor:
 if row[0] == matchValue:
 row[1] = tableValue
 cursor.updateRow(row)