Christophe Pettus: ‘Rollback’ exception added to Xact

I often find that I’m in the middle of a loop or something and discover an error. I want to exit the loop in a way that causes the database work I’ve done within it to be rolled back, but I don’t want that exception to propagate further.

This usually looks like:

try:
   with xact():
      for thing in things:
         (etc. etc.)
 except Rollback:
     pass

Having noticed this pattern a lot, I’ve added it as a feature to Xact. Xact defines a Rollback exception. It processes it like any other exception, but then swallows it and normally exits the function or with clause. If you feel motivated, you can subclass Rollback, although the utility of that escapes me at the moment.

When Django 1.6 is released, Xact will be deprecated in favor of new functionality there… but for now, have fun with it!