引发异常

Question

我有以下代码：

from twisted.internet.defer import Deferred 

def callback1(result): 
    print "callback1 called with ",result 
    return result 

def callback2(result): 
    print "callback2 called with ",result 

def callback3(result): 
    raise Exception("callback 3") 

def errback(result): 
    print 'handled error' 
    return 'everything fine now' 

d = Deferred() 
d.addCallback(callback1) 
d.addCallback(callback2) 
d.addCallbacks(callback3, errback) 
d.callback("Test") 

我期望的输出是：

callback1 called with Test 
callback2 called with Test 
Unhandled Error 
.... 

但我实际上得到的是

callback1 called with Test 
callback2 called with Test 

由于异常在回调链中N级提升由级别为N + 1的errback处理，添加后没有添加错误处理程序回调3，我期待'未处理的异常...'被抛出，但是这并没有发生。我在这里错过了什么吗？

请帮助 谢谢

Answer 1

运行你的榜样，我看到了你的输出预计：

callback1 called with Test 
callback2 called with Test 
Unhandled error in Deferred: 


Traceback (most recent call last): 
    File "t.py", line 21, in <module> 
    d.callback("Test") 
    File ".../twisted/internet/defer.py", line 393, in callback 
    self._startRunCallbacks(result) 
    File ".../twisted/internet/defer.py", line 501, in _startRunCallbacks 
    self._runCallbacks() 
--- <exception caught here> --- 
    File ".../twisted/internet/defer.py", line 588, in _runCallbacks 
    current.result = callback(current.result, *args, **kw) 
    File "t.py", line 11, in callback3 
    raise Exception("callback 3") 
exceptions.Exception: callback 3 

与扭曲的多个版本。你是否真的按原样运行了这个确切的脚本？我假设你重新输入了输出，并没有复制和粘贴，因为你只有一个空间在with和Test之间，而不是实际打印的两个空间。