Brett Slatkin <bslat...@gmail.com> added the comment:
I believe the scope of this bug may be larger than it originally seemed. Now that ProactorEventLoop is the default for Python 3.8 (https://bugs.python.org/issue34687), I'm seeing this same problem on Windows when you try to call asyncio.new_event_loop() from within a thread. It breaks with the ProactorEventLoop (snippet #1 below). It works fine with the SelectorEventLoop (snippet #2 below). Am I wrong to expect to be able to create a unique event loop for each thread from within the thread itself? I worked around this problem by manually forcing the event loop policy (https://bugs.python.org/issue33792). === Snippet #1 (breaks) === import asyncio from threading import Thread def my_func(): asyncio.new_event_loop() t = Thread(target=my_func) t.start() t.join() === Output from snippet #1 === PS G:\> python .\repro.py Exception in thread Thread-1: Traceback (most recent call last): File "C:\Users\User\AppData\Local\Programs\Python\Python38\lib\threading.py", line 932, in _bootstrap_inner self.run() File "C:\Users\User\AppData\Local\Programs\Python\Python38\lib\threading.py", line 870, in run self._target(*self._args, **self._kwargs) File ".\repro.py", line 6, in my_func asyncio.new_event_loop() File "C:\Users\User\AppData\Local\Programs\Python\Python38\lib\asyncio\events.py", line 758, in new_event_loop return get_event_loop_policy().new_event_loop() File "C:\Users\User\AppData\Local\Programs\Python\Python38\lib\asyncio\events.py", line 656, in new_event_loop return self._loop_factory() File "C:\Users\User\AppData\Local\Programs\Python\Python38\lib\asyncio\windows_events.py", line 310, in __init__ super().__init__(proactor) File "C:\Users\User\AppData\Local\Programs\Python\Python38\lib\asyncio\proactor_events.py", line 630, in __init__ signal.set_wakeup_fd(self_no) ValueError: set_wakeup_fd only works in main thread === Snippet #2 (works) === import asyncio from threading import Thread # Work-around from https://bugs.python.org/issue34679 policy = asyncio.get_event_loop_policy() policy._loop_factory = asyncio.SelectorEventLoop def my_func(): asyncio.new_event_loop() t = Thread(target=my_func) t.start() t.join() === More details === My version of Python: 3.8.0b2 (tags/v3.8.0b2:21dd01d, Jul 4 2019, 16:00:09) [MSC v.1916 64 bit (AMD64)] My version of Windows (it's a developer VM from https://developer.microsoft.com/en-us/windows/downloads/virtual-machines): PS G:\> [System.Environment]::OSVersion.Version Major Minor Build Revision ----- ----- ----- -------- 10 0 17763 0 ---------- nosy: +Brett Slatkin _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue34679> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
