Python Asyncio与多线程/多进程那些事

2020-06-19 00:00:00 线程运行调用事件进程

根据asyncio的文档介绍，asyncio的事件循环不是线程安全的，一个event loop只能在一个线程内调度和执行任务，并且同一时间只有一个任务在运行，这可以在asyncio的源码中观察到，当程序调用get_event_loop获取event loop时，会从一个本地的Thread Local对象获取属于当前线程的event loop：

class _Local(threading.local):
    _loop = None
    _set_called = False

def get_event_loop(self):
    """Get the event loop.

    This may be None or an instance of EventLoop.
    """
    if (self._local._loop is None and
            not self._local._set_called and
            isinstance(threading.current_thread(), threading._MainThread)):
        self.set_event_loop(self.new_event_loop())

    if self._local._loop is None:
        raise RuntimeError('There is no current event loop in thread %r.'
                            % threading.current_thread().name)

    return self._local._loop

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