Sorting feature class to calculate sequential ID field using ArcGIS Field Calculator?

Question

I am in ArcMap and I want to sort the records based on a field and then do a Calculate Field with an auto-incrementing value with the sort in-place. Any ideas?

It looks like I could get an update cursor on the feature class then do an auto-increment, but I would still like to see if there is a way to do this in the Field Calculator in ArcMap.

Answer 1

Try using Sort (Data Management) followed by Calculate Field (Data Management) using the auto-increment example on the Calculate Field examples help page.

If you need to sort the data and update it in-place (no intermediate dataset), then I think you would have to use an UpdateCursor which can also sort by a field.

• RyanKDalton: Excellent suggestion. And if you need to do this on a recurring basis, consider linking these tools together in ModelBuilder.
• GeorgeC: The ESRI sample for sequential numbering is based on the FID (original row ID). I want the numbering to be based on the current sort -can this be done? In the code from ESRI what is "global" rec? Thanks.
• blah238: My answer hopefully already answers your first question in two ways: 1) use Sort (Data Management), or 2) use an UpdateCursor with the sort fields argument. I do not think you can access the current table view's sort state through arcpy, though it may be possible through ArcObjects. As for your second question, global makes the variable persist between calculations (one calculation per row) so that it can store the running count used in each calculation.
• user2856: Rather than using the global variable based increment example, you could use itertools.count generator.

Answer 2

I used ModelBuilder and I did a field sort followed by calculate field using the sort code below and it worked great.

Previously, I had tried these two steps outside of ModelBuilder and it failed.

Expression:

autoIncrement()

Expression Type: PYTHON_9.3

Code Block:

rec=0
def autoIncrement():
 global rec
 pStart = 1 #adjust start value, if req'd 
 pInterval = 1 #adjust interval value, if req'd
 if (rec == 0): 
 rec = pStart 
 else: 
 rec = rec + pInterval 
 return rec