Hello everyone,I have this python stand alone script wich is runing fine until gets to this part. if gp.Exists(lcp_name+".shp") == 0: gp.CostPath_sa("samp_lyr", cd_name, bl_name, "cost_path", "BEST_SINGLE", "") # Export the cost of the LCP vat = gp.searchcursor("cost_path") row_n = vat.next() cost1_list = [] while row_n: cost1_list.append(row_n.pathcost) row_n = vat.next() cost1 = sum(cost1_list) del vat, row_n, cost1_list # Turns the raster LCP to a polyline gp.RasterToPolyline_conversion("cost_path","temp.shp", "ZERO", "", "SIMPLIFY") gp.Dissolve_management("temp.shp", lcp_name+".shp") gp.delete_management("temp.shp") gp.delete_management("cost_path") # Calculate the length of the LCP. gp.Addfield_management(lcp_name+".shp", "LENGTH", "DOUBLE") gp.CalculateField_management(lcp_name+".shp", "LENGTH", "float(!SHAPE.LENGTH!)", "PYTHON") gp.Addfield_management(lcp_name+".shp", "COST", "DOUBLE") gp.CalculateField_management(lcp_name+".shp", "COST", cost1, "PYTHON") The error I get is: arcgisscripting.ExecuteError: Error 9999999: Error executing function. The field is not nullable. [COST]. Failed to execute <Calculate field>It creates the field "cost" but doesn't fill it. In ArcMap I open the shape and I'm able to fill it with zero value so I don't understand the error. Any suggestions??Thanks a lot