async.py 文件源码

def __init__(self, callback, callback_time, io_loop=None):
        self.callback = callback
        self.callback_time = callback_time
        self.io_loop = io_loop or IOLoop.current()
        if self.io_loop._running:
            # Use a regular PeriodicCallback
            self._pc = PC(callback, callback_time, io_loop)
        else:
            from threading import Timer
            # NOTE: PeriodicCallback uses ms while Timer uses seconds
            def callback_wrapper():
                "Runs the callback and restarts the Timer so it will run again"
                self.callback()
                self._pc = Timer(callback_time / 1000, callback_wrapper)
                if self._running:
                    self._pc.start()
            self._pc = Timer(callback_time / 1000, callback_wrapper)
        self._running = False