Kyle Stanley <aeros...@gmail.com> added the comment:
FWIW, I agree with get_event_loop() being problematic with its error messages, and having a bit too much functionality in a single function from an API design perspective. It commonly comes up as an issue among asyncio users in communities that I'm active in. Typically, I advise them to use get_running_loop() where possible, as it can be directly substituted within a coroutine func. For __init__ methods, I recommend setting their internal loop attribute to None and then setting it to get_running_loop() in either a coro start() method or coro factory method. Outside of directly managing the event loop, this works for many use cases. When it's needed to actually create one, I advise them to use new_event_loop(), but mention that it's already handled if they're using asyncio.run(). Andrew Svetlov wrote: > The asyncio.get_event_loop() function will stay in Python for a while in > deprecated status. I don't know the exact period but it should be 3 releases > at least I guess, with possibly extending to 5 releases if needed. With how many libraries that rely on it, I suspect it will likely be a very slow transition from deprecation to removal. 4 versions seems like a reasonable period to me, but I think that 3 may be too short (assuming we retain the newer annual release cycle). Yury Selivanov wrote: > I think we still use get_event_loop() in asyncio code, no? Indeed, we currently use it in several places throughout asyncio. From a brief glace using git grep "get_event_loop()": Lib/asyncio/futures.py:76: self._loop = events.get_event_loop() Lib/asyncio/futures.py:390: loop = events.get_event_loop() Lib/asyncio/locks.py:81: self._loop = events.get_event_loop() Lib/asyncio/locks.py:177: self._loop = events.get_event_loop() Lib/asyncio/locks.py:244: self._loop = events.get_event_loop() Lib/asyncio/locks.py:375: self._loop = events.get_event_loop() Lib/asyncio/queues.py:35: self._loop = events.get_event_loop() Lib/asyncio/streams.py:45: loop = events.get_event_loop() Lib/asyncio/streams.py:82: loop = events.get_event_loop() Lib/asyncio/streams.py:104: loop = events.get_event_loop() Lib/asyncio/streams.py:120: loop = events.get_event_loop() Lib/asyncio/streams.py:147: self._loop = events.get_event_loop() Lib/asyncio/streams.py:403: self._loop = events.get_event_loop() Lib/asyncio/subprocess.py:206: loop = events.get_event_loop() Lib/asyncio/subprocess.py:227: loop = events.get_event_loop() Lib/asyncio/tasks.py:69: loop = events.get_event_loop() Lib/asyncio/tasks.py:129: loop = events.get_event_loop() Lib/asyncio/tasks.py:590: loop = events.get_event_loop() Lib/asyncio/tasks.py:669: loop = events.get_event_loop() Lib/asyncio/tasks.py:751: loop = events.get_event_loop() For brevity, I omitted the docs, tests, and the function definition for get_event_loop(). Based on Serhiy's idea (of making get_event_loop() an alias for get_running_loop() without warning inside of a coro func, but warning for using it outside of one), many of the above could remain as is to reduce some code churn. We just have to make sure the documentation is updated to reflect get_event_loop() becoming an alias for get_running_loop(), at the same time as the deprecation warning is added for using it outside of a coro func. Otherwise, I suspect it could lead to significant confusion from users that have warnings enabled. That being said, I think we should eventually remove asyncio.get_event_loop() entirely from the asyncio internals, including the ones that wouldn't raise deprecation warnings (if/when it's made an alias to get_running_loop()) for improved clarity. Personally, I find that even the name get_event_loop() is rather vague; get_running_loop() is much more obvious as to its purpose and what it does from a readability perspective. Yury Selivanov wrote: > If we do, we should start by raising deprecation warnings in those call > sites, e.g. if a Future or Lock is created outside of a coroutine and no > explicit event loop is passed. For asyncio.Lock (plus other synchronization primitives) and asyncio.Queue, this would be added in https://github.com/python/cpython/pull/18195. Currently waiting on emanu (author of the PR) to finish up some changes, but it's mostly complete. Could I work on adding it to asyncio.Future and other classes in the meantime? One point to be clarified though: you mention "created outside of a coroutine and no explicit event loop is passed". However, there are already several deprecations in place for passing an explicit event loop for most (if not all) of the __init__ methods for objects across asyncio's high-level API. In those cases, should the deprecation for creating the object outside of a coroutine function care about whether or not an explicit event loop is passed? I can see why it would matter for the lower level parts of the API (such as asyncio.Future) where passing the event loop explicitly is still allowed, but IMO it shouldn't be a factor for ones where passing the event loop explicitly is already deprecated. Especially considering that the loop argument will be removed from those entirely in 3.10 (according to the version listed in the current deprecation warnings added in 3.8). ---------- nosy: +aeros _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue39529> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
