python 自定義裝飾器

1. 提醒用戶使用了廢棄的函數

def deprecated(func):
    """This decorator is used to mark functions as deprecated.
    It will result in a warning being emitted when the function is used.
    """

    @functools.wraps(func)
    def new_func(*args, **kwargs):
        warnings.simplefilter('always', DeprecationWarning)  # turn off filter
        warnings.warn(
            "Call to deprecated function {}.".format(func.__name__),
            category=DeprecationWarning,
            stacklevel=2
        )
        warnings.simplefilter('default', DeprecationWarning)  # reset filter
        return func(*args, **kwargs)

    return new_func

2. 裝飾類中函數的裝飾器,給函數增加報錯功能

# 裝飾類中函數的裝飾器第一個參數是self
def connection_closed_handler(function):
    """Handle ConnectionClosedException."""
    @wraps(function)
    def _wrap(inst, *args, **kwargs):
        try:
            return function(inst, *args, **kwargs)

        except (ConnectionClosedException, WebSocketConnectionClosedException):
            inst.logger.warn("the connection lost. Resetting ...")
            inst.reset(args[1])
            return function(inst, *args, **kwargs)
    return _wrap

3. 兩層裝飾器寫法

def timelimited(timeout):
    def decorator(function):
        def decorator2(*args, **kwargs):

            class TimeLimited(Thread):
                def __init__(self, _error=None, ):
                    Thread.__init__(self)
                    self._error = _error

                def run(self):
                    try:
                        self.result = function(*args, **kwargs)
                    except Exception as e:
                        self._error = str(e)

                def _stop(self):
                    if self.is_alive():
                        ThreadStop(self)

            t = TimeLimited()
            t.start()
            t.join(timeout)

            if isinstance(t._error, TimeoutException):
                t._stop()
                raise TimeoutException('timeout for %s' % (repr(function)))

            if t.is_alive():
                t._stop()
                raise TimeoutException('timeout for %s' % (repr(function)))

            if t._error is None:
                return t.result
        return decorator2
    return decorator