arcpy: check for same record in cell above and below

Question

After using the find duplicates in arcmap 10, I want to check if the feat sequence ("find duplicates" marks all records with the same attributes with the same number [in "feat_seq"] and creates a ROWID_ that has unique numbers for each record) is the same in the cell above and below and record and if it is the same then mark the duplicate/triplicate etc as "1", if not mark with 0.

The logic we used in excel is =IF(OR(C1=C2,C3=C2),1,0)

If c2 = c1 or c2 =c3, give the cell a value of 1, if not, give the cell a value of 0. Used to identify duplicate values that are in order. If the cell above or below is the same as the cell in question, give the cell a value of 1. If not, give the cell a value of 0.

The code I started to write was

import arcpy
rows = arcpy.UpdateCursor("TestDuplicateID")

for row in rows:
    rowCur=row
    rowPost= row.next()
    rowPre= # how can we get this?


    if rowCur.getValue("FEAT_SEQ")==row.getValue("FEAT_SEQ"):
        rowCur.setValue("Dups", "1")
    elif rowCur.getValue("FEAT_SEQ")==rowPre.getValue("FEAT_SEQ"):
        rowCur.setValue("Dups", "1")
    else:
        rowCur.setValue("Dups","0")

I can't seem to find a way to retain the PRE record and get the following error "Runtime error : unsupported operand type(s) for -: 'Row' and 'int'".

Thanks for your help

Answer 1

Cursors can be tricky, since they only look at one row at a time, and don't like to bounce around arbitrarily. I would sweep through your table twice: once with a SearchCursor, and second with an UpdateCursor.

import arcpy
rows = arcpy.SearchCursor("TestDuplicateID")

# Get first two values
v0 = rows.next().FEAT_SEQ
v1 = rows.next().FEAT_SEQ
# First comparison
unique = [v0 == v1]
# Compare middle rows
for row in rows:
    v2 = row.FEAT_SEQ
    # Middle comparisons
    unique.append(v0 == v1 or v1 == v2)
    # Shift values for next loop
    v0, v1 = v1, v2
# Last comparison
unique.append(v0 == v1)

# Copy the results back to table
rows = arcpy.UpdateCursor("TestDuplicateID")
for i, row in enumerate(rows):
    row.Dups = int(unique[i])
    rows.updateRow(row) 

Answer 2

import arcpy
rows = arcpy.UpdateCursor("TestDuplicateID")

for row in rows:
    rowCur=row
    rowPost= row.next()
    if not rowprev: 'force check to see if rowprev is null (it would be on the first run through the procedure)
        rowprev blah
        rowcur blah
        rownext blah
        'YOUR CODE HERE

    'put this in at the end, so when the first row is through, this gets populated with it
    rowprev = row