On Wed, May 8, 2019 at 2:05 PM Zac Medico <zmed...@gentoo.org> wrote:
> On 5/7/19 1:01 PM, Zac Medico wrote: > > On 5/7/19 7:55 AM, Alec Warner wrote: > > > >> Also curious why we are not implementing enter and exit so we can avoid > >> unbalanced pairs by using context managers. > >> > >> e.g. in match(), we could likely write: > >> > >> with self.dbapi.lock(): > >> # try to match > >> update_pkgindex = self._populate_local() > >> if update_pkgindex: > >> self._pkgindex_write(update_pkgindex) > >> > >> If the block raises an exception, __exit__ is still called, so we can > >> eliminate the finally: blocks and replace them with a careful __exit__ > >> implementation? > >> > >> -A > > > > Yeah, the reference counted lock class could have a method that returns > > a context manager which increments/decrements the lock count. The > > context manager can be implemented with the contextlib.contextmanager > > decorator like this: > > > > @contextlib.contextmanager > > def contextmanager(self): > > self.lock() > > try: > > yield self > > finally: > > self.unlock() > > > > Since we really don't want asynchronous code to block waiting for a > lock, we really should use a (python3.5+ only) asynchronous context > manager: > > > https://www.python.org/dev/peps/pep-0492/#asynchronous-context-managers-and-async-with > > Given that python2.7 is scheduled for retirement in 2020 > (https://pythonclock.org/), maybe it's time to drop support for > python3.4 and earlier. > I haven't used that stuff yet, so I will defer to you on its use; same with python support. -A > -- > Thanks, > Zac > >
