We'll start this chapter with a basic question. What are cursors? Cursors are in-memory objects containing one or more rows of data from a table or feature class. Each row contains attributes from each field in a data source along with the geometry for each feature. Cursors allow you to search, add, insert, update, and delete data from tables and feature classes.

The arcpy data access module or arcpy.da was introduced in ArcGIS 10.1 and contains methods that allow you to iterate through each row in a cursor. Various types of cursors can be created depending on the needs of developers. For example, search cursors can be created to read values from rows. Update cursors can be created to update values in rows or delete rows, and insert cursors can be created to insert new rows.

There are a number of cursor improvements that have been introduced with the arcpy data access module. Prior to the development of ArcGIS 10.1, cursor performance was notoriously slow. Now, cursors are significantly...