topic Re: FeatuerLayer .caculate that concatenates a field with a standalone string in ArcGIS API for Python Questions

FeatuerLayer .caculate that concatenates a field with a standalone string

CameronAndrew — Fri, 01 Dec 2023 21:36:48 GMT

Good afternoon!

I am trying to write a short script that will periodically be run to check whether there are new rows in hosted layer. When there are new rows, I want a particular field to calculated by combing a string prefix ("NNTREE-") with the OBJECTID value. I found some past discussions on .calulate, several which managed to resolve people's problems, but none dealt specifically with trying to combine a field with a string in this way.

import arcgis from arcgis.gis import GIS gis = GIS("pro") trees = gis.content.get('ebc917bcf648444a8161f4dca4afb7ec') trees.layers[0].calculate( where="assetid IS NULL", calc_expression = { 'field': 'assetid', "sqlExpression" :'CONCAT("NNTREE-", OBJECTID)'}) Exception: 'Invalid field: NNTREE-' parameter is invalid (Error Code: 400)

Thank you for any help.

Re: FeatuerLayer .caculate that concatenates a field with a standalone string

EarlMedina — Mon, 04 Dec 2023 15:13:50 GMT

Hey, your calc_expression value should be:

{"field": "assetid", "sqlExpression": "CONCAT('NNTREE-', OBJECTID)"}

Re: FeatuerLayer .caculate that concatenates a field with a standalone string

CameronAndrew — Thu, 07 Dec 2023 13:54:41 GMT

That' great, thank you. I had managed a slightly more convoluted workaround to achieve the same effect, but this is preferable. I appreciate your help!

Looks like it was just the single/double quotation marks at issue? As someone primarily accustomed to R, I need to get used to there being an important distinction between those two characters in SQL syntax.