On Sat, Sep 17, 2011 at 5:38 PM, Chris Angelico <ros...@gmail.com> wrote: > But if it's done as an exception, all you need is to > catch that exception and reraise it: > > def threadWork(lock, a1, a2, rate): > try: > while True: > time.sleep(rate) > lock.lock() > t = a2.balance / 2 > a1.balance += t > #say a thread.kill kills at this point > a2.balance -= t > lock.release() > except: > # roll back the transaction in some way > lock.release() > raise
And what if the thread gets killed a second time while it's in the except block? > It'd require some care in coding, but it could be done. And if the > lock/transaction object can be coded for it, it could even be done > automatically: > > def threadWork(lock, a1, a2, rate): > while True: > time.sleep(rate) > transaction.begin() > t = a2.balance / 2 > transaction.apply(a1.balance,t) > #say a thread.kill kills at this point > transaction.apply(a2.balance,-t) > transaction.commit() > > If the transaction object doesn't get its commit() called, it does no > actions at all, thus eliminating all issues of locks. And what if the thread gets killed in the middle of the commit? Getting the code right is going to be a lot more complicated than just adding a couple of try/excepts. Cheers, Ian -- http://mail.python.org/mailman/listinfo/python-list
