Cursors and Field calculation - Python 2.5 - ArcGis 9.3

Question

I hope my question is not redundant.

I wrote a script to Update a table using two imbricate cursors. The goal was 1) to read a records, update some of its values 2) Make a selection based on this record (e.g. closest neighbors) 3) Update the neighbors

I have first tried using two imbricate update cursors like the following:

rows = gp.UpdateCursor(Infile)
row = rows.Next() 
while row:
    # Read InFile attribute
    val = row.GetValue(Attribute)
    #  Update some attributes
    val = row.SetValue(Field, function(val))
    # Select Neighbors
    gp. gp.GANeighborhoodSelection(Infile, Layer, Condition related to val)
    //.....//
    # Update Neighbors
    urows = gp.UpdateCursor(Infile)
    urow = urows.Next() 
    while urow:
        #  Update some attributes
        val = urow.SetValue(Field, function(val))
        urows.UpdateRow(urow)
        urow = urows.Next() 
    del urow, urows
    //.....//
    row.UpdateRow(row)
    row = rows.Next()
    //.....//

Using such a code, the second update cursor was calculating correctly (i printed some intermediate results) but the calculation was not applied to the table (ie. not physical updation).

I modified the code by replacing the second update cursor by a Select by attributes followed by a calculate field. Again, the calculations were not applied to the table. I think there is a lock problem somewhere but I did not found how to solve the problem.

Finally, I replaced my first UpdateCursor by a SearchCursor and then used an UpdateCursor based on a condition in order to reduce the number of record processed. The code look like this:

rows = gp.SearchCursor(Infile)
row = rows.Next() 
while row:
    # Read InFile attribute
    val = row.GetValue(Attribute)
    #  Update some attributes
    val = row.SetValue(Field, function(val))
    # Select Neighbors
    gp. gp.GANeighborhoodSelection(Infile, Layer, Condition related to val)
    //.....//
    # Update Neighbors
    urows = gp.UpdateCursor(Infile, Condition based on val)
    urow = urows.Next() 
    while urow:
        #  Update some attributes
        val = urow.SetValue(Field, function(val))
        urows.UpdateRow(urow)
        urow = urows.Next() 
    del urow, urows
    //.....//
    row.UpdateRow(row)
    row = rows.Next()
    //.....//

Using such a structure, all is working fine. However, calculation is longer (around 5 sec. for 1000 records).

Do you have any idea 1) why using 2 imbricate UpdateCursor is not working and 2) how to use select by attributes and calculate field within a cursor to fasten the calculation?

Thanks a lot

Cedric

Answer 1

You haven't used the updateRow method.

while urow:
    #  Update some attributes
    val = urow.SetValue(Field, function(val))
    urows.updateRow(urow) 
    urow = urows.Next()