Question

    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()

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

感谢。

Answer 1

它从未被调用过，因为你的评论中的代码表示它要求反应堆在 4 秒内停止运行实际上要求反应堆在 1 秒内停止运行。永远不会调用2秒callLater，因此永远不会触发d，因此永远不会调用nextCall。

也许您应该尝试在不使用reactor的情况下构建此示例，只需在适当的延迟上同时调用callback？你不需要反应器来触发一个简单的Deferred，同时搞乱它们可以帮助你更准确地了解什么时候会发生什么。

如何在扭曲的延迟回调中捕获异常？

1 个答案: