Calculate Field - VB to Python

Question

I have a Calculate Field module in a Model that used the following VB expression in ArcGIS v9.0. Now that I am trying to run this same model in V10 it does not work??

Dim Area as double
Dim pArea as IArea
Set pArea = [shape]
Area = pArea.area/10000

Any idea why it does not work?  Should I be converting to Python so that it works in v10?  Any insight on how to convert the above code to python.

Thank

BruceLang · Answer

!Shape.Centroid.X!

See the field calculator help here for more on geometry calculation in ArcGIS 10.  Also the Python syntax was incorrect in the post above.  The exclamations points go around the Shape qualifiers as shown above.  So !Shape.FirstPoint.X! might also work, but it would not return the same result as your original VBA calculation, since that is returning the Centroid.

Excellent!  Using !Shape.Centroid.X! for longitude, and !Shape.Centroid.Y! for latitude work perfectly.  Now the calculate field properties (for longitude) in my model are:* Input Table: Work_anno
* Field Name: Longitude
* Expression: !Shape.Centroid.X!
* Expression Type: PYTHON_9.3
* Code Block: (empty)

Now my geoprocessing model for exporting an annotation feature to a points shapefile works as before. :cool:

Thank you.

RichardFairhurst · Answer

Additional Information:

The following knowledge base article describes the procedure   HowTo: Convert an annotation feature class to a shapefile

But the following error is displayed.  
Executing (Calculate Field (2)): CalculateField "\hcgis1\gis\Arc\Projects\WTH\Work_Area\Work Data.gdb\Work_Anno" Longitude Output VB "Dim Output As Double
Dim pArea As IArea
Set pArea = [Shape]
Output = pArea.Centroid.X"
Start Time: Wed Dec 28 09:08:27 2011
General error executing calculator.
ERROR 999999: Error executing function.
Expected end of statement
Failed to execute (Calculate Field (2)).
Failed at Wed Dec 28 09:08:30 2011 (Elapsed Time: 3.00 seconds)

The same error displays when attempting the calculation; (1) directly on the field (i.e. Field Calculator) in an edit session, and (2) With the "Calculate Field" tool in my model - FYI the model "used" to work at 9.3.1.

Thanks in advance.

You cannot do geometry calculations with VB Script at ArcGIS 10. VBA is no longer available in the field calculator and shape variables are not supported in VB Script. (VBA and VB Script are similar, but have key differences that prevent you from doing geometry calculations with VB Script at ArcGIS 10).

You have to convert to Python to do geometry calculations in the field calculator. Because you are using Centroid you cannot access the coordinate with the FirstPoint option. For Area based objects you probably need to use Centroid (at least for something odd like Annotation, it might work with a true Polygon, which has a starting point).

!Shape.Centroid.X!

See the field calculator help here for more on geometry calculation in ArcGIS 10. Also the Python syntax was incorrect in the post above. The exclamations points go around the Shape qualifiers as shown above. So !Shape.FirstPoint.X! might also work, but it would not return the same result as your original VBA calculation, since that is returning the Centroid.

BruceLang · Answer

Additional Information:

The following knowledge base article describes the procedure HowTo: Convert an annotation feature class to a shapefile

But the following error is displayed.
Executing (Calculate Field (2)): CalculateField "\hcgis1\gis\Arc\Projects\WTH\Work_Area\Work Data.gdb\Work_Anno" Longitude Output VB "Dim Output As Double
Dim pArea As IArea
Set pArea = [Shape]
Output = pArea.Centroid.X"
Start Time: Wed Dec 28 09:08:27 2011
General error executing calculator.
ERROR 999999: Error executing function.
Expected end of statement
Failed to execute (Calculate Field (2)).
Failed at Wed Dec 28 09:08:30 2011 (Elapsed Time: 3.00 seconds)

The same error displays when attempting the calculation; (1) directly on the field (i.e. Field Calculator) in an edit session, and (2) With the "Calculate Field" tool in my model - FYI the model "used" to work at 9.3.1.

Thanks in advance.