pg.py 文件源码

def __init__(self, db, event, callback=None,
            arg_dict=None, timeout=None, stop_event=None):
        """Initialize the notification handler.

        You must pass a PyGreSQL database connection, the name of an
        event (notification channel) to listen for and a callback function.

        You can also specify a dictionary arg_dict that will be passed as
        the single argument to the callback function, and a timeout value
        in seconds (a floating point number denotes fractions of seconds).
        If it is absent or None, the callers will never time out.  If the
        timeout is reached, the callback function will be called with a
        single argument that is None.  If you set the timeout to zero,
        the handler will poll notifications synchronously and return.

        You can specify the name of the event that will be used to signal
        the handler to stop listening as stop_event. By default, it will
        be the event name prefixed with 'stop_'.
        """
        self.db = db
        self.event = event
        self.stop_event = stop_event or 'stop_%s' % event
        self.listening = False
        self.callback = callback
        if arg_dict is None:
            arg_dict = {}
        self.arg_dict = arg_dict
        self.timeout = timeout