Setting values in feature class attribute table to null

Question

I've created a point-data feature class (fc) containing data from a simple .txt file using ArcPy as follows:

arcpy.CreateFeatureclass_management(out_path= outPath, out_name= 'fcTest', geometry_type= "POINT", spatial_reference= spatRef, has_m= m, has_z= z)

I've read the text file to create fields and fill each field with data:

#lstFields= data from the text file
#fNames= list of fieldnames
#fClass= list of datatypes
for i in range(len(fNames)):
    arcpy.AddField_management(fcTest, fieldN, fieldT)

Let's say the .txt file contains the xy coordinates and two fields: fA and fB

with arcpy.da.InsertCursor('fcTest', ("SHAPE@XY", "fA", "fB")) as cursor: 
    for point in lstFields: 
        vals= point.split(";")
        x= float(vals[0])
        y= float(vals[1])
        a= int(vals[2])
        b= float(vals[3])
        rowValue= [(x, y), a, b]
        cursor.insertRow(rowValue)

So far so good. However, some values of fA and fB have value 9999, which actually means 'no data'.

How do I convert the 9999 values to a 'real' NoData value?

I thought

setNull(field_name)

might be it, but I can't get it to work. See ArcGIS help here. I tried something like:

with arcpy.da.UpdateCursor('fcTest', ("fA", "fB")) as cursor:
    for row in cursor:
        for i in range(len(row)):
            if row[i] == 9999:
                row.setNull(row[i])
                cursor.updateRow(row)
except Exception as e:
    print e.message

Which gives:

'list' object has no attribute 'setNull'

I'm new to ArcPy and have based most of the above on the Programming ArcGIS10.1 with Python Cookbook by E. Pimpler.

---

This works flawlessly:

with arcpy.da.UpdateCursor('fcTest', ("fA", "fB")) as cursor:
    for row in cursor:
        for i in range(len(row)):
            if row[i] == 9999:
                row[i] = None
                cursor.updateRow(row)
except Exception as e:
    print e.message

Answer 1

You could try:

if row[i] == 9999:
   row[i] = None
   cursor.updateRow(row)

Answer 2

The original error is indicating that setNull is not a method for arcpy.da.UpdateCursor, but it is a method for arcpy.UpdateCursor (no "da").