pointZ and getZ

brucesimonson

Hi Gang,

I'm chasing myself into corners, trying to add a field to a PointZ shapefile, that contains the hidden Z value associated with the shape.  Can't get it to work.  I expect a Python snippet like this to work, in field calculator, for example:

[Shape].Z

But I get nothing but errors.

Huh?
-Bruce

RichardFairhurst

Both of the above suggestions work great, when run from the attribute table.  I'd like to extend this, though, to creating a python program which reads all of the shapefiles in a workspace, adds a field for z, and updates with the appropriate value.

For example, in a set of shapefiles that have PointZ values in meters, I'd like to add a field which captures the Z value in feet (from the source shapefiles, which are in meters).  Not sure why I can't get this to work:

import arcpy
from arcpy import env

env.workspace = "P:/path/to/some/directory"

fcList = arcpy.ListFeatureClasses( )

for fc in fcList:
    arcpy.AddField_management( fc, "Z_feet", "DOUBLE", "10", "3" )
    arcpy.CalculateField_management(fc, "Z_feet", "3.28083 * float(!SHAPE.CENTROID.Z!)", "PYTHON")

In particular, !SHAPE.CENTROID.Z! seems to work in the field calculator (Python mode), but not in a Python program.

Suggestions?

Change "PYTHON" in your calculation to "PYTHON_9.3".  "PYTHON" is pre-9.3 and does not use the current syntax of the field calculator.  A new Python keyword was created so that "PYTHON" would remain unchanged for pre-9.3 scripts to maintain backward compatibility.

Additionally you don't need to cast to float and you don't need to do the multiplication to convert to Feet.  Change the calculation to:

!SHAPE.CENTROID.Z@FEET!