I hope my question is not redundant.
I wrote a script to Update a table using two imbricate cursors. The goal was:
- to read a records, update some of its values
- Make a selection based on this record (e.g. closest neighbors)
- 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:
- why using 2 imbricate UpdateCursor is not working; and
- how to use select by attributes and calculate field within a cursor to fasten the calculation?
I'm using Python 2.5 and ArcGIS Desktop 9.3
