pipeline.py 文件源码

def on(event, callback):
    """Call `callback` on `event`

    Register `callback` to be run when `event` occurs.

    Example:
        >>> def on_init():
        ...    print("Init happened")
        ...
        >>> on("init", on_init)
        >>> del on_init

    Arguments:
        event (str): Name of event
        callback (callable): Any callable

    """

    if event not in _registered_event_handlers:
        _registered_event_handlers[event] = weakref.WeakSet()

    events = _registered_event_handlers[event]
    events.add(callback)