topic Re: Update cursor and SHAPE@XY token problem in New to GIS Questions

Update cursor and SHAPE@XY token problem

PanagiotisChiotis — Mon, 11 May 2015 12:44:38 GMT

Hello everyone,

I am new to Python and ArcPy.

I am testing the script below which is running for a point feaure class, but not for a line feature class.

import arcpy
arcpy.env.workspace = r"D:\Student\PYTH\6_Geometry_objects\SanDiego.gdb"
# Variables
featClass = "MajorAttractions2"
fields = ["SHAPE@XY"]
exp = "OBJECTID = 4"
pnt = arcpy.Point()
pnt.X = 306400
pnt.Y = 4098400
with arcpy.da.UpdateCursor(featClass, fields, exp) as cur:
for row in cur:
row[0] = pnt
cur.updateRow(row)
print "Script completed"

In the latter case, I am getting the following error message: "exceptions.SystemError: error return without exception set" for line 16.

Thank you in advance,

Panagiotis

Re: Update cursor and SHAPE@XY token problem

DarrenWiens2 — Mon, 11 May 2015 20:34:24 GMT

Ignoring the fact that you are trying to create a line from a single point (which surprisingly works), does the line feature class contain a feature at OBJECTID = 4?

Re: Update cursor and SHAPE@XY token problem

PanagiotisChiotis — Mon, 11 May 2015 22:11:51 GMT

Hello Darren,

I am not trying to create a line feature class, but rather shift a feature of it. Both point and line feature classes already exist. And, yes, "OBJECTID = 4" is a valid expression in both cases.

Regards,

Panagiotis

Re: Update cursor and SHAPE@XY token problem

OwenEarley — Mon, 11 May 2015 23:21:56 GMT

SHAPE@XY for a line feature will return the feature centroid. You will need to use SHAPE@ and then locate the vertex point on the polyline to update.

These pages have more detail:

Reading geometries - ArcGIS Help (10.2, 10.2.1, and 10.2.2)
Writing geometries - ArcGIS Help (10.2, 10.2.1, and 10.2.2)

Re: Update cursor and SHAPE@XY token problem

DarrenWiens2 — Mon, 11 May 2015 23:27:16 GMT

I thought you had to do it vertex by vertex, too, but this post seems to disagree: https://arcpy.wordpress.com/2012/11/15/shifting-features/

It shifts geometry all as one.

Re: Update cursor and SHAPE@XY token problem

OwenEarley — Mon, 11 May 2015 23:53:01 GMT

Good catch - I hadn't seen that post.

Re: Update cursor and SHAPE@XY token problem

DanPatterson_Retired — Tue, 12 May 2015 00:13:46 GMT

exp = "OBJECTID = 4" are you sure it is a valid where clause, it looks like an assignment statement, did you try
exp = "OBJECTID == 4"

Re: Update cursor and SHAPE@XY token problem

DarrenWiens2 — Tue, 12 May 2015 00:27:01 GMT

1. Should be correct through SQL goggles.

Re: Update cursor and SHAPE@XY token problem

DanPatterson_Retired — Tue, 12 May 2015 00:50:11 GMT

sigh.... python googles always on

Re: Update cursor and SHAPE@XY token problem

JoshuaBixby — Tue, 12 May 2015 02:54:15 GMT

You didn't catch it because documenting important functionality like that on a third-party blogging platform is, well, poor taste. It would be nice and a bit more enterprise-y if the ArcGIS Python development team did more blogging within an Esri domain, say GeoNet maybe.

Re: Update cursor and SHAPE@XY token problem

JoshuaBixby — Tue, 12 May 2015 03:11:46 GMT

The "SHAPE@XY" token doesn't return an ArcPy Point object, it returns "a tuple of the feature's centroid x,y coordinates." Line 15 of your code replaces a Python tuple with an ArcPy Point object, which is what I am guessing is causing the error on Line 16. Does the code work if you update Line 15 to:

row[0] = (306400, 4098400)

Re: Update cursor and SHAPE@XY token problem

PanagiotisChiotis — Tue, 12 May 2015 10:17:52 GMT

Hello Joshua,

You are right, I was thinking that the tuple of a feature's centroid X&Y coordinates could be replaced by a Point object (which stores coordinate pairs of X&Y values). And yes, the code works when I updated Line 15 to:

row[0] = (306400, 4098400)

However, for some funny reason, it works fine when running the script for a point feature class .

Anyway, thanks a lot, it really cleared things up!

Best regards,

Panagiotis