Calculating centroids of polygon using ArcPy?

Question

I am trying to calculate the centroids of a polygon and add the x- and y-coordinate to their respective fields:

arcpy.env.workspace = r"C:/..."
input_fc = "shapefiles/precincts_v.shp"
arcpy.AddField_management(input_fc, "X", "DOUBLE")
arcpy.AddField_management(input_fc, "Y", "DOUBLE")
arcpy.CalculateField_management(input_fc, "X", "!SHAPE.CENTROID@DECIMALDEGREES!.split()[0]", "PYTHON") 
arcpy.CalculateField_management(input_fc, "Y", "!SHAPE.CENTROID@DECIMALDEGREES!.split()[1]", "PYTHON") 

but I an invalid syntax error. Where is the mistake?

Edit: exact error message

Traceback (most recent call last):
 File "C:\Users\mquentel\Dropbox\PLSS\CA voting data\Python\CONSTRUCT_merge_voting_and_census.py", line 17, in <module>
 arcpy.CalculateField_management(input_fc, "X", "!SHAPE.CENTROID@DECIMALDEGREES!.split()[0]", "PYTHON")
 File "C:\Program Files (x86)\ArcGIS\Desktop10.4\ArcPy\arcpy\management.py", line 3360, in CalculateField
 raise e
ExecuteError: ERROR 000539: SyntaxError: invalid syntax (<expression>, line 1)
Failed to execute (CalculateField).

• Kristen G.: I don't immediately see any "syntax" errors. Can you post the exact error that you're getting?
• Hornbydd: Also it is unhelpful when you replace the true code with some generic message as you have for the variable input_fc. How do we know that is not what you have actually run? If it is it is invalid, you need the full path or have set the geoprocessing workspace environment setting which we see neither.
• eigenvector: I have updated the exact error message. Thank you for the hint, Kristen G. Unfortunately, there is no new information in there, is it? What else information could I provide? What else could I test?
• eigenvector: Thank you for your comment, Hornbydd. I have added the "true" code. However, I find the downvote (if its related) rather unfair. With any problem and asking for advice it is always a balance between providing too few or providing too much code. If it helps you detect the error, though, fair enough.
• BritishSteel: Have you tried using PYTHON_9.3 instead of PYTHON (last parameter)?

Answer 1

Replace your Field Calculator lines with

arcpy.CalculateField_management(input_fc, "X", "!SHAPE.CENTROID.X!", "PYTHON_9.3")
arcpy.CalculateField_management(input_fc, "Y", "!SHAPE.CENTROID.Y!", "PYTHON_9.3")

Works for me with Decimal Degrees.

• eigenvector: Thank you for the suggestion. This seems to give me the following error: ExecuteError: ERROR 000539: Error running expression: GPVARIANTOBJECT0.CENTROID.X Traceback (most recent call last): File "<expression>", line 1, in <module> SystemError: error return without exception set Failed to execute (CalculateField). Any idea why?
• Clubdebambos: Does your file have a Shape field? Try using RepairGeometry_management first as per gis.stackexchange.com/questions/127232/… and then try again to get the centroids
• eigenvector: Thanks for the suggestions and the linked question. My shapefile has a shape field. And using RepairGeometry_management before did not change anything. Is there anything else I can do to get a clue what is going wrong?
• Clubdebambos: Is it possible to provide a zipped file of the shapefile or a sample of the data?
• eigenvector: I found a workaround with a similar (but different) shapefile. Your code works perfectly fine now. My problem was ultimately rooted in the broken shapefile which even could not be repaired with the RepairGeomety_management (good suggestion, though!). In any case, it is fixed now. Thank you.