topic Re: Cursor Not Working in Python Questions

Cursor Not Working

alysaochoa2 — Fri, 18 Nov 2016 15:59:19 GMT

Hi everyone,

I'm writing a script to plot points and then delete rows that have a value of less than 5.

I am getting the following error on the cursor lines:

Traceback (most recent call last):
File "C:\Users\30030839\Favorites\Downloads\pyfinal2.py", line 32, in <module>
cursor = arcpy.da.UpdateCursor("C:\\Users\\30030839\\Desktop\\Python\\capacity_points_layer2", ["DEM"])
RuntimeError: cannot open 'C:\Users\30030839\Desktop\Python\capacity_points_layer2'

I'm not sure why this file isn't able to open. It's not being used in any application, and its folder is not open.I added the file to ArcMap previously to make sure the shapefile worked and that the attribute table exists, and it's fine. Does anyone know why I would be getting this error?

Re: Cursor Not Working

NeilAyres — Fri, 18 Nov 2016 16:07:29 GMT

So, what is this layer you are trying to run an update cursor on?

cursor = arcpy.da.UpdateCursor("C:\\Users\\30030839\\Desktop\\Python\\capacity_points_layer2", ["DEM"])

It is not a shapefile, nor anything in a file geodatabase, so what is it and does it exist.

Re: Cursor Not Working

alysaochoa2 — Fri, 18 Nov 2016 16:12:07 GMT

It’s a .lyr file. To test, I added it to ArcMap to make sure it worked. It seems like everything is fine and it should work. I also tried the cursor with .lyr and it did not help.

[cid:image002.png@01D2417B.CC5CC3A0]

Re: Cursor Not Working

NeilAyres — Fri, 18 Nov 2016 16:16:18 GMT

Well, then it should have ".lyr" on the end as the extension. Do yourself a favour and in the file explorer, view setting untick to options which says "hide extensions for known file types".

But, I think an update cursor should be run on the data itself. Not a layer file which is a superset (including defrinitions and symbology) and a pointer to the data itself.

So, where is the feature you are trying to update and what is it?

Re: Cursor Not Working

alysaochoa2 — Fri, 18 Nov 2016 16:21:09 GMT

The feature I am trying to update is saved in this path on my computer: C:
Users
30030839
Desktop
Python
capacity_points_layer2.lyr

It is a point shapefile. I have attached the point shapefile if that helps.

Regards,

Re: Cursor Not Working

alysaochoa2 — Fri, 18 Nov 2016 16:25:19 GMT

Now I got it to recognize the file but I’m getting a different error:

All of the script seems logical and the file works fine. This is the first time I’m running into this problem, where the cursor is not working and I am not getting much information from the IDLE on why.

Re: Cursor Not Working

MitchHolley1 — Fri, 18 Nov 2016 17:20:32 GMT

Can you post the updated code, please?

Re: Cursor Not Working

alysaochoa2 — Fri, 18 Nov 2016 18:23:42 GMT

Here is the updated script. I have tested ALL other parts of the script and it works. Just the cursor is not working.

According to this source from Esri, I should be able to just reference the layer to update the rows in the table. UpdateCursor—ArcPy Functions | ArcGIS for Desktop

Re: Cursor Not Working

DarrenWiens2 — Fri, 18 Nov 2016 18:27:10 GMT

Rather than pointing the cursor to the .lyr file, can you try pointing it to the feature class that the .lyr refers to?

Re: Cursor Not Working

MitchHolley1 — Fri, 18 Nov 2016 18:27:57 GMT

Try this:

with arcpy.da.UpdateCursor(newLayer, [field1]) as cursor:

Put the field variable in brackets.

Re: Cursor Not Working

alysaochoa2 — Fri, 18 Nov 2016 19:16:32 GMT

Hi All,

Converting my layer to a feature class and referencing that feature class in the cursor worked!

Thank you so much for all of your help.

-AO

Re: Cursor Not Working

alysaochoa2 — Fri, 18 Nov 2016 19:21:21 GMT

Final completed script with no errors:

Re: Cursor Not Working

JoshuaBixby — Sat, 19 Nov 2016 00:55:00 GMT

You are misunderstanding the documentation. A "layer" and "layer file" are not synonymous. Cursors can work on datasets directly or layers/views of datasets, cursors do not work directly against layer files. If you want to use a layer file, first use Make Feature Layer (if spatial) or Make Table View to create a layer and then pass that layer to the cursor.