topic Re: arcpy.UpdateCursor setting a row value to null instead of 0 in Python Questions

arcpy.UpdateCursor setting a row value to null instead of 0

ShaneArmour — Wed, 23 Sep 2015 22:42:53 GMT

Hi,

I'm having issues setting a row value to 0 when joining a csv to a shapefile. When the shapefile value is not in the csv, the row is getting set to 0 instead of null. This is a huge problem as i'm showing 0 change instead of no data. I tried row.setValue(field, None) and row.setNull(field) and both produce the same result. In the .dbf file of the shapefile, there is no value but in the UI attribute table a 0 is shown. Any advice on how to fix this would be very appreciated.

Thanks!

Shane

arcpy.AddField_management(shpfile, "TEST", "DOUBLE", field_is_nullable = 'NULLABLE')

newcols = ["TEST"]

with open(csvfile, 'rb') as csvfile:

lib = dict()

csvfile = csv.reader(csvfile, delimiter = ",")

csvfile.next() #skip the headers

for line in csvfile:

lib[line[csvjoinindex]] = lib.get(line[csvjoinindex],line[csvstartfield:])

rows = arcpy.UpdateCursor(shpfile)

for row in rows:

shpjoinval = str(row.getValue(shapefilejoincol))

try:

vals = lib.get(shpjoinval)

for ind, field in enumerate(newcols):

row.setValue(str(field),vals[ind])

rows.updateRow(row)

except:

for ind, field in enumerate(newcols):

row.setNull(field)

rows.updateRow(row)

Re: arcpy.UpdateCursor setting a row value to null instead of 0

FreddieGibson — Wed, 23 Sep 2015 23:05:20 GMT

You'd need to use a geodatabase feature class instead of a shapefile to accomplish this. Shapefiles do not support NULL values. This is documented on the following page:

Add Field (Data Management)

http://desktop.arcgis.com/en/desktop/latest/tools/data-management-toolbox/add-field.htm

As shown in the screenshot below, Null values are only supported for fields in a geodatabase.

Re: arcpy.UpdateCursor setting a row value to null instead of 0

DanPatterson_Retired — Wed, 23 Sep 2015 23:47:57 GMT

specifics to shapefiles regarding nulls or lack thereof

Data type containing null value	Null value substitution
Number—When tool requires that a NULL, infinity, or NaN (Not a Number) be output	-1.7976931348623158e+308 (IEEE standard for the maximum negative value)
Number (all other geoprocessing tools)	0
Text	" " (blank—no space)
Date	Stored as zero, but displays <null>

from here Geoprocessing considerations for shapefile output—Help | ArcGIS for Desktop