I've got a python script that runs on the Field Calculator of a ESRI File Database. Right now it runs correctly in that it will increment the last three digits of the value. But this is a script that is run as part of post processing so it will be run everytime there are new entries in the feature class. My question is how can I modify this so that every time it runs it will look at the last four digits of the FacilityID and increment from there below is a screenshot of my attribute table:

enter image description here

EDIT: And below is my Python script I need to modify.

cur = arcpy.SearchCursor("Telecommunications Line")
fac_id_values = [int(row.FACILITYID[-4:]) for row in cur]

maximum_value = max(fac_id_values)
if maximum_value:
 rec= maximum_value 
 rec = 0

def autoIncrement(): 
 global rec 
 pStart = 1  
 pInterval = 1 
 if (rec == 0):  
  rec = pStart  
  rec += pInterval  
 return "COMLI" + "11" +  format(rec, '03d')

Ok after running the code above I got this as a result. It overwrote the previous values as shown above. The First item should have a FacilityID of COMLI111001. enter image description here

1 Answer 1


You can loop through the FC first and find them maximum value.


import arcpy
nullvalues = ["", " ", None, 0]
# Loop through and get Max value
cur = arcpy.SearchCursor("Telecommunications Line")
fac_id_values = [int(row.FACILITYID[-4:]) for row in cur if row.FACILITYID not in nullvalues]

max_value = max(fac_id_values)

# Loop through and Calculate new values
cur = arcpy.UpdateCursor("Telecommunications Line")
for row in cur:
    max_value = max_value + 1
    if row.FACILITYID in nullvalues:
        row.FACILITYID = "COMLI1" + str(format(max_value,'04d'))

This should ensure that you only update Null values.

  • list comprehensions are awesome! Commented May 9, 2014 at 18:23
  • Yes, this could all be put into 1 line, but for readablity, i chose to seperate it into 3. max_value = max([int(row.FACILITYID[-4:]) for row in arcpy.SearchCursor("YOUR FC")])
    – dklassen
    Commented May 9, 2014 at 18:27
  • I'm always a fan of readability, and the list comprehension allowed you to take what would be even more verbose language, compress it to a single line, and still end up with three highly readable lines. Features like these make me enjoy working with Python after toiling for too long with Javascript ;) Commented May 9, 2014 at 18:31
  • Totally agree!!
    – dklassen
    Commented May 9, 2014 at 18:37
  • So I was going to implement this so if Maximum_value is not null then set rec=maximum_value right?
    – yams
    Commented May 9, 2014 at 19:17

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