topic slicing error in python in ArgGIS 10.4.1 for desktop in Python Questions

slicing error in python in ArgGIS 10.4.1 for desktop

EvanD — Tue, 01 Jan 2019 22:18:47 GMT

I am attempting to run a script that throws an error in a seemingly simple statement in bold below:

for i in range(1,len(part)):
cut=part[i-1:i+1]
sides.append(arcpy.Polyline(cut,SR))

I ran the script up to where part is defined then entered:

>>> part
<Array [<Point (2524240.5113, 2562562.7555, #, #)>, <Point (2524240.8774, 2562712.7555, #, #)>, <Point (2524290.3774, 2562712.6347, #, #)>, <Point (2524290.0113, 2562562.6347, #, #)>, <Point (2524240.5113, 2562562.7555, #, #)>]>
>>> c = part[0:2]
Runtime error
Traceback (most recent call last):
File "<string>", line 1, in <module>
File "c:\program files (x86)\arcgis\desktop10.4\arcpy\arcpy\arcobjects\mixins.py", line 161, in __getitem__
return convertArcObjectToPythonObject(self._arc_object.GetObject(index))
AttributeError: Array: Error in parsing arguments for GetObject

I have tried on two computers, one with python 3 also installed and one without. The python directories returned by sys.path are all there (although the path also includes the non-existent 'C:\\WINDOWS\\SYSTEM32\\python27.zip').

Any ideas on how to troubleshoot this? Thanks.

Re: slicing error in python in ArgGIS 10.4.1 for desktop

DanPatterson_Retired — Tue, 01 Jan 2019 23:01:52 GMT

The array needs getObject to access the individual points. The supported properties and methods are listed in the help

Array—ArcPy classes | ArcGIS Desktop

Re: slicing error in python in ArgGIS 10.4.1 for desktop

JoshuaBixby — Sat, 11 Dec 2021 14:58:27 GMT

Are you running 10.4.1 or 10.4? Prior to 10.4.1, ArcPy geometry objects did not support indexing and slicing. I believe that included ArcPy array objects as well, but I don't have access to a 10.4 machine to test.

Your code works fine in 10.6.x, and I believe it will also work fine in 10.5.x:

>>> import arcpy
>>> coords = [
...   (2524240.5113, 2562562.7555),
...   (2524240.8774, 2562712.7555),
...   (2524290.3774, 2562712.6347),
...   (2524290.0113, 2562562.6347),
...   (2524240.5113, 2562562.7555)
... ]
>>> 
>>> part = arcpy.Array(arcpy.Point(*coord) for coord in coords)
>>> part
<Array [<Point (2524240.5113, 2562562.7555, #, #)>, <Point (2524240.8774, 2562712.7555, #, #)>, <Point (2524290.3774, 2562712.6347, #, #)>, <Point (2524290.0113, 2562562.6347, #, #)>, <Point (2524240.5113, 2562562.7555, #, #)>]>
>>> part[0:2]
<Array [<Point (2524240.5113, 2562562.7555, #, #)>, <Point (2524240.8774, 2562712.7555, #, #)>]>
>>> 
>>> c = part[0:2]
>>> 
‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Re: slicing error in python in ArgGIS 10.4.1 for desktop

EvanD — Thu, 03 Jan 2019 22:03:47 GMT

It says 10.4.2.5686.

Re: slicing error in python in ArgGIS 10.4.1 for desktop

JoshuaBixby — Thu, 03 Jan 2019 23:53:16 GMT

Build 5686 is 10.4.1 final. Although My Esri states my enhancement requests for geometry slicing was implemented in 10.4.1, it could be wrong and 10.5 instead. I know it works in 10.6.1, so the question remains what version exactly does it start working.

Re: slicing error in python in ArgGIS 10.4.1 for desktop

DanPatterson_Retired — Sat, 11 Dec 2021 14:58:30 GMT

It has worked in Pro since I can remember... the arcpy's differ though

import arcpy
coords = [(2524240.5113, 2562562.7555), (2524240.8774, 2562712.7555), (2524290.3774, 2562712.6347), (2524290.0113, 2562562.6347), (2524240.5113, 2562562.7555) ]
part = arcpy.Array(arcpy.Point(*coord) for coord in coords)

part
<Array [<Point (2524240.5113, 2562562.7555, #, #)>, <Point (2524240.8774, 2562712.7555, #, #)>, <Point (2524290.3774, 2562712.6347, #, #)>, <Point (2524290.0113, 2562562.6347, #, #)>, <Point (2524240.5113, 2562562.7555, #, #)>]>

part[:2]
<Array [<Point (2524240.5113, 2562562.7555, #, #)>, <Point (2524240.8774, 2562712.7555, #, #)>]>

pnts = [p for p in part]

pnts
[<Point (2524240.5113, 2562562.7555, #, #)>, <Point (2524240.8774, 2562712.7555, #, #)>, <Point (2524290.3774, 2562712.6347, #, #)>, <Point (2524290.0113, 2562562.6347, #, #)>, <Point (2524240.5113, 2562562.7555, #, #)>]

arr = np.asarray([(p.X, p.Y) for p in part])
arr
array([[2524240.5113, 2562562.7555],
       [2524240.8774, 2562712.7555],
       [2524290.3774, 2562712.6347],
       [2524290.0113, 2562562.6347],
       [2524240.5113, 2562562.7555]])

np.mean(arr, axis=0)
array([2524260.45774, 2562622.70718])‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍