I'm fairly new to python, so I'm having a little trouble with this. I want to iterate through a list of values, select the list values from a feature class, select from another feature class that intersects the first selection, and then calculate a field in the second selection based of the list index value. Here's the script I'm working on:

import arcpy
arcpy.env.workspace = r"C:workspace.gdb"

circuits = ["DC430", "DC431", "DC432"]

for i in range(len(circuits)):
    arcpy.SelectLayerByAttribute_management("Meters", "NEW_SELECTION", circuits[i])
    arcpy.SelectLayerByLocation_management("Parcels", "INTERSECT", "Meters", "", "NEW_SELECTION", "NOT_INVERT")
    arcpy.CalculateField_management("Parcels", "Circuit", "circuits[i]", "PYTHON_9.3", "")

How do I make this work the right way?

  • Select works on Layer. So use make feature layer and use SQL inside. Use select by location on newly created layer.
    – FelixIP
    Mar 16, 2018 at 0:06

1 Answer 1


Iterate through your list of circuits and then create an SQL that matches the format you'd see in an ArcMap selection.

For text fields in a file geodatabase:


Your code would be something like this:

import arcpy
arcpy.env.workspace = r"C:workspace.gdb"

circuits = ["DC430", "DC431", "DC432"]
circuitFieldName = "YOURFIELDNAMEHERE"

for circuit in circuits:
    sql = "{} = '{}'".format (circuitFieldName, circuit)
    arcpy.SelectLayerByAttribute_management("Meters", "NEW_SELECTION", sql)
    arcpy.SelectLayerByLocation_management("Parcels", "INTERSECT", "Meters")
    arcpy.CalculateField_management("Parcels", circuitFieldName, '"{}"'.format (circuit))
  • Create layer is missing.
    – FelixIP
    Mar 16, 2018 at 0:06
  • @ecartrace don’t forget to mark the answer as correct then. Mar 17, 2018 at 6:01
  • Hi sir, I know my comment is too late. But would you care to explain what the "{} = '{}'".format is please? It seems like I see it on this sub from time to time. What's it called and how can I read up more on it? Thanks.
    – Bowen Liu
    Sep 5, 2018 at 13:36
  • @Emil The first part of the string format() sql expression has the correct syntax, i.e., the quotes are correct - good work, and thanks! Jun 17, 2020 at 5:45

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