topic Re: How to get the last element of a polyline array? in Python Questions

How to get the last element of a polyline array?

MennoNijhuis1 — Mon, 01 Jul 2013 15:40:01 GMT

To my surprise, it is impossible to get the last element of an array from a polyline (which is a arcpy.arcobjects.arcobjects.Array, so not a normal Python array for which it would definitely work!).

my_array[-1]

throws this error:

Runtime error <type 'exceptions.RuntimeError'>: Array: Error in getting object from array

EDIT:

OK a rather stupid workaround I thought of myself:

my_array.getObject(len(my_array)-1)

gives:

<Point (280349.568, 311663.817, #, 162.393)>

I still wonder: why is it not possible to just use my_array[-1]

Re: How to get the last element of a polyline array?

markdenil — Mon, 01 Jul 2013 18:09:19 GMT

As you point out, an arcpy.arcobjects.arcobjects.Array is not a normal Python array,
so it doesn't index nicely.
As a geometry object, however, it has a lastPoint property, which should be simple to access.

Re: How to get the last element of a polyline array?

ShaunWalbridge — Mon, 01 Jul 2013 18:49:47 GMT

You could subclass arcpy.Array to include a __getitem__ method, and then handle slicing and indexing there, if you want to be Pythonic about accessing the elements. However, Mark's solution is probably the simplest answer.

cheers,
Shaun

Re: How to get the last element of a polyline array?

MennoNijhuis1 — Tue, 02 Jul 2013 08:02:14 GMT

I hadn't even thought of accessing the geometry object, focussed as I was with accessing the array. This will work nicely, thanks both!