Create sequential numbers in a field in ArcMap using Python in the Field Calculator

Summary

Instructions provided describe how to create sequential numbers in a field in ArcMap using Python in the Field Calculator.

Procedure

Note:
The code in this article generates sequential numbers for unsorted data based on the OID or FID order. If the data is sorted on a field, the generated numbers are not sequential.

1. Create a new short integer field. Refer to ArcMap: Adding fields for instructions.
2. Right-click the new field and select Field Calculator.
3. Set the Parser to Python.
4. Check the check box for Show Codeblock.
5. Paste the following into the Pre-Logic Script Code:

rec=0 
def autoIncrement(): 
 global rec 
 pStart = 1  
 pInterval = 1 
 if (rec == 0):  
  rec = pStart  
 else:  
  rec += pInterval  
 return rec

6. Paste the following code in the smaller box below the Pre-Logic Script Code:

autoIncrement()

7. Click OK. The following image is an example of a field with sequential numbers populated using the Python code: