Sum rows of a field

Discussion created by rgthurau on Nov 23, 2011
Latest reply on Nov 23, 2011 by rgthurau
I'm trying to create a single scalar value as the sum of a row, then use the scalar in a field calculation:

I want the sum of "UTC10_FT" call it tot_utc_ft, then use that value in a calculate field:

to find the sum value:

list2 = []
rows = arcpy.SearchCursor(fc)
for row in rows:
    utc_ft = row.getValue("UTC10_Ft")
    tot_utc_ft = sum(list2)

arcpy.CalculateField_management(parcels, "Tot_UTC_Pct", """!UTC10_Ft! / tot_utc_ft""", "PYTHON")

Currently getting this error:
    tot_utc_ft = sum(list)
TypeError: unsupported operand type(s) for +: 'float' and 'NoneType'

I'm sure this is something simple, but admittedly, not a great python programmer.

The next question will be whether python will use my tot_utc_ft variable within field calculator? Or, do I need to perform this operation within an expression?

Thanks for your help.