引發異常

Question

我有以下代碼：

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") 

我期望的輸出是：

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

但我實際上得到的是

callback1 called with Test 
callback2 called with Test 

由於異常在回調鏈中N級提升由級別爲N + 1的errback處理，添加後沒有添加錯誤處理程序回調3，我期待'未處理的異常...'被拋出，但是這並沒有發生。我在這裏錯過了什麼嗎？

請幫助 謝謝

Answer 1

運行你的榜樣，我看到了你的輸出預計：

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 

與扭曲的多個版本。你是否真的按原樣運行了這個確切的腳本？我假設你重新輸入了輸出，並沒有複製和粘貼，因爲你只有一個空間在with和Test之間，而不是實際打印的兩個空間。