Best way to handle exceptions with try/finally

[Roy Smith]

In article <1148457332.582609.98490 at 38g2000cwa.googlegroups.com>,
 "Maxim Sloyko" <m.sloyko at gmail.com> wrote:

> I guess the following standard method will help :
> 
> class MyLocker(object):
>     def __init__(self, lock):
>           self.lock = lock
>           self.lock.acquire()
> 
>     def __del__(self):
>         self.lock.release()
> 
> Then whenever you need to acquire a lock:
> templock = MyLocker(self.__mutex)
> 
> del templock # will release the lock (provided you didn't create an
> extra link to this object)

Warning!  Danger, Will Robinson!  Evil space aliens are trying to write C++ 
in Python!  Quick, we must get back to the ship before they eat our brains!

The problem here is that there is no guarantee that __del__() will get 
called at any predictable time (if at all).  C++ uses deterministic object 
destruction.  Python doesn't destroy (finalize?) objects until the garbage 
collector runs.

See PEP-343 (http://www.python.org/dev/peps/pep-0343/) for the new "with" 
statement which should solve problems like this.  If I understand things 
right, "with" will be included in Python-2.5, which is due out Real Soon 
Now.