How To: Create sequential numbers in a field using Python in the Field Calculator

Summary

Instructions provided describe how to create sequential numbers in a field 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 will not be sequential.

1. Create a new short integer field.
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:
   

Related Information

• ArcMap Help: Adding fields
• ArcMap Help: Fundamentals of field calculations
• ArcMap Help: Making simple field calculations
• ArcMap Help: Calculate Field examples