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. -- Thanks, Zac
signature.asc
Description: OpenPGP digital signature
