[GIS] Use Round in ArcMap 10.x Field Calculator on field with both numeric and NULL values

arcgis-10.1field-calculator

With older versions of ArcMap (9.3, 9.2, etc) I was always able to round numbers down to 2 decimal places using field calculator even if that field had both numeric values and a bunch of NULL values. It used to just ignore the NULL values. With ArcGIS 10.x this is no longer the case.

round([UPSTREAMINVERT],2)

Rounding a field that has any NULL values leads to error 999999, error executing function – invalid use of Null: 'round'

I realize it works just fine when you remove NULL values from the selection. However, I'd prefer not to have to do this for every field I'd like to have rounded.

Has anyone else experienced this and found a work-around? I've tried to do an if-then statement in field calculator to only return the rounded value if the value is not NULL. This gives the same error message.

Thanks.

Best Answer

I think python uses None instead of Null as in other languages..It Could be the issue. You could do a check if

fieldValue is None

before rounding.

Related Solutions

[GIS] Getting Null value error with Python Parser in field calculator

This is a quick and easy way to get around the problem..but doesn't fix the error. This method works in the python window.

This design is often used inside of loops, and I'm unsure if the Field Calculator will accept it.

try:
 #the code you want to work goes here

except: #handles the error
    #print "an error occurred, but I can continue to work"
    pass

[GIS] Calculate Fields with Null Values using arcpy.da.UpdateCursor of ArcGIS for Desktop

Here's a way to replace all the nulls with zeroes:

import arcpy
with arcpy.da.UpdateCursor(r"...gdb\test.gdb\test",["A", "B", "C"]) as cursor:
    for row in cursor:
        a_value = row[0] if row[0] else 0  # Use 0 when "A" is falsy
        b_value = row[1] if row[1] else 0  # Use 0 when "B" is falsy
        row[2] = a_value + b_value
        cursor.updateRow(row)

Note: this doesn't actually update the null values in the table; it merely replaces them with zeroes during calculations. If you want to replace the nulls with zeroes permanently, you could change the penultimate line to row = [a_value, b_value, a_value + b_value].

Best Answer

Related Solutions

[GIS] Getting Null value error with Python Parser in field calculator

[GIS] Calculate Fields with Null Values using arcpy.da.UpdateCursor of ArcGIS for Desktop

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