ArcGIS do calcuation on multiple input fields of attribute table and the number of input fields is changing

Question

I have attribute table with headers: ID(bgrp), F1 (F2011_46), F2 (F2011_48), ...Fn

I want to do math calculations on the fields from F1 to Fn. For example, count the total number of non-zero Fn fields for each ID unit. Normally, a field calculator using python script will do the job. But the problem is n vary each time and I have many such tables, so I don't know if I should modify the input fields each time when do field calculation for one such table. Additionally, n is usually large, 30 to 100, and I don't think it is efficient to manually select all the Fn fields in a Pre-Logic Script Code.

Answer 1

Here is an answer, but it's a bit hacky... halfway between Field Calculator and true arcpy tool:

def CalcThis(YourID):
    YourFeatClassOrLayerName = "Polylines" # Change this to your layer name
    desc = arcpy.Describe(YourFeatClassOrLayerName)

    fList = arcpy.ListFields(YourFeatClassOrLayerName,"L*") # List of matching fields, in this case fields starting with L
    fRange = range(len(fList))
    sumNonNull = 0
    # field names into list of string
    fNameList = []
    for f in fList:
        fNameList.append(f.name)

    with arcpy.da.SearchCursor(YourFeatClassOrLayerName,fNameList,desc.OIDfieldName + " = " + str(YourID)) as sCur:
        for sRow in sCur:
            for thisIndex in fRange:
                if sRow[thisIndex] != None:
                    sumNonNull += 1

    return sumNonNull

This script gets a list of matching fields, the OIDfieldName for the feature class (important later) then turns the field list into a list of strings for arcpy.da.SearchCursor - with a query on just one row! then increments if the field is not None (NULL) and returns that. Considering how sloppy it is it's still reasonably fast.