Arcpy Code: Find duplicate values in an ArcGIS feature class field

I'm finding coding in arcpy a little more frustrating than I would like and decided to share useful code here in case it helps anyone else trying to the same or similar things.


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# identifyduplicates.py
# Created by: Mairead de Roiste, Victoria University of Wellington
# Date: 16 Feb 2012
# What does it do?: prints to screen a list of the values that are
# duplicates in a particular field in an ArcGIS feature class
###########################################

# Import arcpy module
import arcpy

# set up variables
# the feature class you want to sort then search
fc = "D:\\ISCR_transport\\code\\data\\NZTA_workhomepoints\\workhomepoints.gdb\\workloc"

# field to sort in ascending order
fieldname = "FIRST_uniquePerson"fieldascend = fieldname + " A"

# create UpdateCursor to search through the rows, field above sorted in ascending order
rows = arcpy.SearchCursor(fc,"","","", fieldascend)

#Create an empty list
dupValuesList = []

# the code needs to be updated for the name of the field
i = -1
for row in rows:
    if i == -1: #first time around       
        value = row.FIRST_uniquePerson
        i += 1
        print value, i
    elif row.FIRST_uniquePerson != value: #if a new ID       
        value = row.FIRST_uniquePerson
        i = 0
    else:
        dupValuesList.append(value)
print dupValuesList