如何在扭曲的延迟回调中捕获异常？答案

【问题标题】：How to catch exception in twisted Deferred callback?如何在扭曲的延迟回调中捕获异常？
【发布时间】：2023-03-13 07:56:02
【问题描述】：

    from twisted.internet import reactor, defer

def getDummyData(x):
    """
    This function is a dummy which simulates a delayed result and
    returns a Deferred which will fire with that result. Don't try too
    hard to understand this.
    """
    d = defer.Deferred()
    # simulate a delayed result by asking the reactor to fire the
    # Deferred in 2 seconds time with the result x * 3
    reactor.callLater(2, d.callback, x * 3)
    return d

def printData(d):
    """
    Data handling function to be added as a callback: handles the
    data by printing the result
    """
    raise ValueError('IIIGGAA')
    print d

def nextCall(d):
    import pdb; pdb.set_trace()
d = getDummyData(3)

d.addErrback(nextCall).addCallback(printData).addErrback(nextCall).addCallback(nextCall)


# manually set up the end of the process by asking the reactor to
# stop itself in 4 seconds time
reactor.callLater(1, reactor.stop)
# start up the Twisted reactor (event loop handler) manually
reactor.run()

function nextCall - 从不调用。那么我能找到我的 ValueError 吗？

谢谢。

【问题讨论】：

标签： python twisted deferred

【解决方案1】：

它从未被调用，因为您的注释下的代码要求反应堆在 4 秒内自行停止，实际上是要求反应堆在 1 秒内自行停止。 2 秒的callLater 永远不会被调用，所以d 永远不会被触发，所以nextCall 永远不会被调用。

也许您应该尝试在不使用反应器的情况下构建这个示例，只需在适当的 deferred 上同步调用callback？您不需要反应器来触发简单的Deferred 并同步处理它们可以帮助您更准确地了解何时发生的确切情况。

【讨论】：