UpdateCursor won't update concatenated string?

Question

I have a function I'm trying to incorporate in a model. It's supposed to check to see if one of two fields have a value and depending on the field with value calculate the other.

The issue I'm having is writing the result back into my feature using the UpdateCursor. I don't have any experience using it, and not sure if it's the right tool for the job. Here's my function:

import arcpy

upCursor = arcpy.da.UpdateCursor("SepticTankPermit layer", ['pid','pidgis'])

def autoCheck():
 with arcpy.da.SearchCursor("SepticTankPermit layer",['pid','pidgis']) as cursor:
 for row in cursor:
  if row[0] is 'NULL' or row[0] == '':
    pidgis = row[1]
    upCursor.updateRow([pidgis[:2]+'-'+pidgis[4:6]+'-'+pidgis[6:7]+'-'+pidgis[7:10]+'-'+pidgis[10:13]+'.'+pidgis[13:]],[pidgis])
  elif row[1] is 'NULL' or row[1] == '':
    pid = row[0]
    upCursor.updateRow([pid],[pid[:2]+'00'+pid[3:5]+ pid[6:7]+ pid[8:11]+ pid[12:15]+ pid[16:]])
  else:
    print "PID or PIDGIS must have a value in order to execute properly!"

I'm not sure if I'm using it correctly.

Answer 1

There are a couple things wrong with this code snippet. First, you don't need to specify a SearchCursor just to look through a table. The UpdateCursor has the ability to read row values and update through a single iteration. Secondly, when assigning a value to a row, you need to set the index of the field to the value (row[1] = row[0][:2] + ' pid') based on the index set in the cursor (line 2). Lastly, the UpdateCursor updates rows one at a time after each iteration... meaning you set the values of each field, then update the entire row (cursor.updateRow(row)) specified in line 3.

import arcpy
with arcpy.da.UpdateCursor("SepticTankPermit layer",['pid','pidgis']) as cursor:
    for row in cursor:
        if row[0] in [None,'','NULL']:
            row[0] = row[1][:2]  #etc...
        elif row[1] in [None,'','NULL']:
            row[1] = row[0][:2] #etc...
        else:
            print "Row not updated..."
        cursor.updateRow(row)
del cursor