Sqlalchemy delete, update or keep row in large dataset

I'm working on simple but large dataset in sqlite using sqlalchemy. I need to iterate over all rows in a table and based on some business logic either update, delete or keep the row.

Because of the size of my data I used the code from http://ift.tt/1MyQbOy to page my query data. The code works fine as long as no rows are deleted during the processing. Otherwise it will skip over some data.

What is the proper solution using sqlalchemy?