I have a table in a file geodatabase that has "FieldA" and "FieldB".

I want to update FieldB with one of two values, depending on if there are one or more records with the same value of FieldA.


FieldA   FieldB

   1        0

   2        1

   2        1

   3        0

I've tried this way

with arcpy.da.UpdateCursor(featureClass, ("FieldA", "FieldB")) as cursor:

for rupd in cursor:

    rows = [row for row in arcpy.SearchCursor(featureClass, 'FieldA=' + str(rupd[0]) )]

    if len(rows)>1:


The table has around 100k records. It takes around 1 second each record.

Can this performance be improved?


Your code is slow because you have nested cursors so for each row in the updatecursor you are creating a searchcursor and reading rows. You are also using the old searchcursor (not da.) which is slow.

Instead first count all occurences once using collections.Counter. The result is is a dictionary with FieldA value as key and count as value, for example: {1:1, 2:2, 3:1}.

...an unordered collection where elements are stored as dictionary keys and their counts are stored as dictionary values.

import arcpy
from collections import Counter

fc = r'C:\data.gdb\featureclass'
field1 = 'FieldA'
field2 = 'FieldB'

#Store count for each FieldA value in a dictionary
cnt = Counter()
with arcpy.da.SearchCursor(fc, field1) as cursor:
    for row in cursor:

#For every row check count in dictionary and update FieldB
with arcpy.da.UpdateCursor(fc,[field1, field2]) as cursor:
    for row in cursor:
        if cnt[row[0]]>1:
  • 1
    Never used the counter. Great tip. Thank you so much. – Rui Neves May 29 '19 at 20:48

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