topic Re: How do I resolve warning 002858? in Python Questions

How do I resolve warning 002858?

KatieMichel — Tue, 28 Jul 2020 18:58:44 GMT

Hi, I'm trying to find the percent change of temperature using two climate projections with the formula %change=((new-old)/old)*100. When running it through "calculate field" this is what I have:

and I get this warning message with all of my values returned as null:

Any ideas?

Re: How do I resolve warning 002858?

DanPatterson — Tue, 28 Jul 2020 23:09:22 GMT

It is a warning... one of your two fields has a null value in it, so when it tries to perform the numerator operation, it is either getting

a number - None

None - a number

So you will have to fix your data if you aren't expecting nulls in those fields, or you will have to fix the expression to deal with nulls.

In any event, a warning probably didn't make all the calculations fail did it?

Re: How do I resolve warning 002858?

IssamAchour — Mon, 20 Jun 2022 16:52:34 GMT

yeah how to perform calculations and you have NULL values? i have these kinds of data since this information aren't reported so it must be involved in my geoprocessing work

how to deal with that using python?

Re: How do I resolve warning 002858?

RyanBohan — Wed, 06 Aug 2025 22:09:51 GMT

Python treats null values as none. And python can't add to nothing.
Attribute1 = null
Attribute2 = 5

Current State:
Attribute1 + Attribute1 =
none + 5 = null

To handle Nulls:
Use or include a default value
(!Attribute1! or 0) + (!Attribute2! or 0) =
0 + 5 = 5

Or use arcade:
$feature.Attribute1 + $feature.Attribute2 =
null + 5 = 5

Re: How do I resolve warning 002858?

bcgeogirl1 — Mon, 02 Feb 2026 17:02:29 GMT

This is how I fixed this problem when I had it.

%change=(((new or 0)-(old or 0))/(old or 0))*100

it puts in a 0 where the values are null. Hope it helps you