I am trying to write a script where you preemptively select features and then go to the tool which calls for the feature layer and it populates fields based on certain criteria which I will design of the selected features.

I am simply trying to populate fields right now using the Update Cursor, but the field still come up blank.

here is my code so far:

input= arcpy.GetParameterAsText(0)

fields= ['Conf','Com']
with arcpy.da.UpdateCursor(input,fields) as cursor:
    for row in cursor:
        row[0] == '2'
        del row
    del cursor

Why are the selected features, or any feature for that matter not updated?

  • 5
    Do not del row. row[0]='2'. Also do not use word input, do not del cursor
    – FelixIP
    Commented Jan 18, 2016 at 0:45

1 Answer 1


To expand more on @FelixIP comment, your row[0] is not assigning a value since double "==" are used with a if conditional statement for evaluating a value to be true or false. Use single "=" for committing a value change instead. Also, since your cursor is used within a with loop you do not need to delete the cursor and row objects.

Try this instead for your example:

fc = arcpy.GetParameterAsText(0)
fields = ['Conf','Com']
    with arcpy.da.UpdateCursor(fc,fields) as cursor:
        for row in cursor:
            row[0] = '2'

To update only selected features you will have to make the input fc a feature layer first (use MakeFeatureLayer method) and then perform a Select Layer By Attribute or Select Layer By Location method before entering the cursor.


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