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I have a large script in which I now need to sum the values of a specific list of fields. I have a list of fields:

ave_fields = arcpy.ListFields(dg, "*Ave_STG*")

This list of fields may vary, hence why im using a list, and not explicit field names.

Now, all I need to do is sum the values in these fields for each row and return this value into another field ("weekly_ave").

Ive tried using SearchCursor:

with arcpy.da.SearchCursor(dg, ave_fields) as ucursor:
    total = 0
    for urow in ucursor:
        for i in range(0, len(ave_fields)):
            total += urow[i]
    print total

And ive also tried using NumpyArray to get this, but its not returning the right value:

tbl = [row[0] for row in arcpy.da.TableToNumPyArray(dg,ave_fields)]

This is my first attempt at using Numpy so I may not have got this right.

EDIT:

I have managed to get the numpy array to work properly, however i now need to return this value in the new field

tbl = arcpy.da.FeatureClassToNumPyArray(dg, ave_fields)

print sum(tbl[0]) # this allows me to sum a row within the array

#now i loop through each row and sum the values within the array, and return this value in the weekly_ave field for each row
with arcpy.da.UpdateCursor(dg, "Weekly_Ave") as ucursor:
    for urow in ucursor:
        print sum(tbl[0]) # this successfully sums the row, but i need to do this for all rows

I get the following error:

TypeError: unsupported operand type(s) for +: 'int' and 'numpy.ndarray'
  • Sum(urow) is enough, but instead of list of fields you'll need their names – FelixIP Aug 7 '17 at 10:07
  • Ive managed to get the array to work using ListFields method. However i cant loop through each row properly. – MacroZED Aug 7 '17 at 13:13
3

I'd add the weekly_ave field to your list of fields for your update cursor and then use indexing to sum and update your row accordingly.

ave_fields = [f.name for f in arcpy.ListFields(dg, "*Ave_STG*")]
with arcpy.da.UpdateCursor(dg, ave_fields + ["weekly_ave"]) as ucursor:
    for urow in ucursor:
        row [-1] = sum (row [:-1])
        ucursor.updateRow (row)
  • 1
    +1 however first row should produce field Names. [F.name for f in...] – FelixIP Aug 7 '17 at 22:04
  • @FelixIP good point. Updated. – Emil Brundage Aug 7 '17 at 22:10

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