New submission from Mark Dickinson:
In the new asyncio library, it's easy for newbies (like me) to accidentally try
to run a coroutine on a closed event loop. Doing so leads to a rather
inscrutable exception and traceback:
>>> loop.run_until_complete(compute())
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File
"/opt/local/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/asyncio/base_events.py",
line 203, in run_until_complete
self.run_forever()
File
"/opt/local/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/asyncio/base_events.py",
line 184, in run_forever
self._run_once()
File
"/opt/local/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/asyncio/base_events.py",
line 778, in _run_once
event_list = self._selector.select(timeout)
AttributeError: 'NoneType' object has no attribute 'select'
Is it possible to replace this with something clearer? For example, something
like: RuntimeError("Can't schedule coroutine on closed event loop.")
Here's the full code snippet:
Python 3.4.0 (default, Mar 25 2014, 11:07:05)
[GCC 4.2.1 Compatible Apple LLVM 5.1 (clang-503.0.38)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import asyncio
>>> @asyncio.coroutine
... def compute():
... print("Starting computation")
... yield from asyncio.sleep(2.0)
... print("Complete")
...
>>> loop = asyncio.get_event_loop()
>>> loop.run_until_complete(compute())
Starting computation
Complete
>>> loop.close() # whoops
>>> # some time later
...
>>> loop = asyncio.get_event_loop()
>>> loop.run_until_complete(compute())
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File
"/opt/local/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/asyncio/base_events.py",
line 203, in run_until_complete
self.run_forever()
File
"/opt/local/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/asyncio/base_events.py",
line 184, in run_forever
self._run_once()
File
"/opt/local/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/asyncio/base_events.py",
line 778, in _run_once
event_list = self._selector.select(timeout)
AttributeError: 'NoneType' object has no attribute 'select'
----------
components: Library (Lib)
messages: 216994
nosy: gvanrossum, mark.dickinson
priority: normal
severity: normal
stage: needs patch
status: open
title: asyncio: request clearer error message when event loop closed
type: enhancement
versions: Python 3.5
_______________________________________
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue21326>
_______________________________________
_______________________________________________
Python-bugs-list mailing list
Unsubscribe:
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
