Python 扭曲'；s trap方法引发的异常不'；不要被抓住

在我看来，failure.trap方法引发了无法用try/except块捕获的异常

from twisted.internet import defer


def someAsynchronousMethod(_):
    print 'I am an asynchronous method and I raise a ZeroDivisionError!!!'
    raise ZeroDivisionError

def __errorHandler(failure):
    print 'I am __errorHandler number 1 !!!!'
    try:
        # Traps only NameError, other Errors will be immediately reraised
        failure.trap(NameError)

        # This code executes only if Exception has been trapped
        ret = {'errno': 666,
               'errmsg': 'NameError'
               }

    # It looks like this code will be executed if Exception has not been trapped
    # instead it was reraised and should be caught here, but it turns out it
    # doesn't get caught, instead the method returns None at this point
    except Exception:
        # This code is never reached
        ret = {'errno': 5000,
               'errmsg': 'OtherError'
               }

    # This code is reached if Exception has been trapped
    return ret

def __successHandler(result):
    print 'Successful execution !!!!'
    return result


def __successHandler2(result):
    print """I expect to receive ret = {'errno': 5000, 'errmsg': 'OtherError'},
          because __errorHandler number 1 is supposed to return a dict !!!!"""
    return result


def __errorHandler2(failure):
    print 'I am __errorHandler number 2 !!!!'
    return failure


d = defer.Deferred()

# Method that raises an Error
d.addCallback(someAsynchronousMethod)

d.addCallbacks(__successHandler, __errorHandler)

d.addCallbacks(__successHandler2, __errorHandler2)

d.callback(0)

输出：

我是一个异步方法，我提出了一个错误！！！
我是一号错误处理者！！！！
我是2号错误处理者！！！！
延迟中未处理的错误：
未处理错误
回溯（最近一次呼叫最后一次）：
文件“twistedFailures.py”，第58行，在
d、 回调（0）
回调中的文件“/usr/local/lib/python2.7/dist-packages/twisted/internet/defer.py”，第382行
自启动返回（结果）
文件“/usr/local/lib/python2.7/dist-packages/twisted/internet/defer.py”，第490行，在startRunCallbacks中
self.\u runCallbacks（）
---  ---
文件“/usr/local/lib/python2.7/dist-packages/twisted/internet/defer.py”，第577行，在运行回调中
current.result=回调（current.result，*args，**kw）
文件“twistedFailures.py”，第8行，在someAsynchronousMethod中
调零误差
异常。零错误：

我期望failure.trap方法引发的任何异常都会被捕获，但我错了

---

Twisted在幕后有什么具体的方法来处理这个问题吗？如果是，原因是什么？

您预期

失败。陷阱
重新引发
零分区错误
异常。但这只发生在Python3中：在Python2中，
failure.trap
实际上重新引发了
failure
。政府对此非常清楚：

在Python 2中，将引发故障；在Python3中，将重新引发底层异常

Twisted的类不从继承，因此您的
异常除外：
不会捕获它。您需要
而不是（异常、失败）：

I am an asynchronous method and I raise a ZeroDivisionError!!!
I am __errorHandler number 1 !!!!
I am __errorHandler number 2 !!!!
Unhandled error in Deferred:
Unhandled Error
Traceback (most recent call last):
  File "twistedFailures.py", line 58, in <module>
    d.callback(0)
  File "/usr/local/lib/python2.7/dist-packages/twisted/internet/defer.py", line 382, in callback
    self._startRunCallbacks(result)
  File "/usr/local/lib/python2.7/dist-packages/twisted/internet/defer.py", line 490, in _startRunCallbacks
    self._runCallbacks()
--- <exception caught here> ---
  File "/usr/local/lib/python2.7/dist-packages/twisted/internet/defer.py", line 577, in _runCallbacks
    current.result = callback(current.result, *args, **kw)
  File "twistedFailures.py", line 8, in someAsynchronousMethod
    raise ZeroDivisionError
exceptions.ZeroDivisionError: