On Fri, Jul 5, 2013 at 2:38 AM, Steven D'Aprano <steve+comp.lang.pyt...@pearwood.info> wrote: > On Thu, 04 Jul 2013 15:47:57 +1000, Chris Angelico wrote: >> Here's one example of shadowing that comes from a C++ project at work. I >> have a class that represents a database transaction (constructing it >> begins a transaction, it has methods for doing queries, and its >> destructor rolls back). > > When the object finally gets garbage collected, doesn't that mean the > last transaction will be rolled back?
Oh. Uhm... ahh... it would have helped to mention that it also has a commit() method! But yes, that's correct; if the object expires (this is C++, so it's guaranteed to call the destructor at that close brace - none of the Python vagueness about when __del__ is called) without commit() being called, then the transaction will be rolled back. And since this is PostgreSQL we use, the same applies if the process is SIGKILLed or the power fails. If commit() doesn't happen, neither does the transaction. (There are a few actions the program can take that are deliberately non-transactional - log entries of various sorts, mainly - but everything else is guarded in this way.) ChrisA -- http://mail.python.org/mailman/listinfo/python-list
