@djangoproject · Post #95 · 2016/07/11 12:14
https://docs.python.org/3/library/asyncio-dev.html#asyncio-multithreading 18.5.9.3. #Concurrency and #multithreading An event loop runs in a thread and executes all callbacks and tasks in the same thread. While a task is running in the event loop, no other task is running in the same thread. But when the task uses yield from, the task is suspended and the event loop executes the next task. To schedule a callback from a different thread, the BaseEventLoop.call_soon_threadsafe() method should be used. Example: loop.call_soon_threadsafe(callback, *args) Most asyncio objects are not thread safe. You should only worry if you access objects outside the event loop. For example, to cancel a future, don’t call directly its Future.cancel() method, but: loop.call_soon_threadsafe(fut.cancel) To handle signals and to execute subprocesses, the event loop must be run in the main thread. To schedule a coroutine object from a different thread, the run_coroutine_threadsafe() function should be used. It returns a concurrent.futures.Future to access the result: future = asyncio.run_coroutine_threadsafe(coro_func(), loop) result = future.result(timeout) # Wait for the result with a timeout The BaseEventLoop.run_in_executor() method can be used with a thread pool executor to execute a callback in different thread to not block the thread of the event loop. See also The Synchronization primitives section describes ways to synchronize tasks. The Subprocess and threads section lists asyncio limitations to run subprocesses from different threads.
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