Calculating "None" Using Field Calculator Yields "WARNING 003571"

VinceE

Experienced this in ArcGIS Pro 3.0.2. Couldn't replicate in 2.9.

I was recently setting some values to NULL using Field Calculator. Expression type is Python 3, value I am inputting is None. To be clear, I'm typing in None without quotes or anything extra. Just the Python data type None. This used to set all values in the field to Esri's NULL, represented as <Null>. Standard stuff.

However now this operation yields the following:

[WARNING 003571: Certain rows set to NULL due to error while evaluating python expression: Cannot be evaluated to value.]

To be clear, the operation still works--highlighted rows in the specified field (tested with SHORT and TEXT fields) still evaluate to NULL. I'm just curious what the function of this warning is. Is there now a preferred way of setting values to NULL? If this Python expression results in an evaluation "error," as stated in the warning  message, why does it still work? Is there something that has changed here that I should be aware of? Am I missing something?

Thanks in advance if anyone has any insight into this bizarre change.

Robert LeClair

Vince - from what I've learned in the internals:

Resolution:

- Reached out to our internal team and it was confirmed that Warning: 003571 is an expression validation that was added at 3.0 as the datatype being calculated and the datatype of the field is different. Although it does not affect the output that you get, still ArcGIS Pro 3.0 would produce this warning.
- None is NoneType and not String which makes sense for a Text field. The same warning appears if you try applying a tuple to a string field. See our internal note on this below: "The expression can be valid python code, say "3,2" (a tuple two integers) but not be a valid value for the target field. Historically this would result in a Null value getting PUT into the row. At Pro 3.0 this is still the case however we produce a warning."

Hope this helps!