twisted.python.failure.Failure : API documentation

A basic abstraction for an error that has occurred.

This is necessary because Python's built-in error mechanisms are inconvenient for asynchronous communication.

The stack and frame attributes contain frames. Each frame is a tuple of (funcName, fileName, lineNumber, localsItems, globalsItems), where localsItems and globalsItems are the contents of locals().items()/globals().items() for that frame, or an empty tuple if those details were not captured.

Instance Variable	value	The exception instance responsible for this failure.
Instance Variable	type	The exception's class.
Instance Variable	stack	list of frames, innermost last, excluding `Failure.__init__`.
Instance Variable	frames	list of frames, innermost first.
Method	__init__	Initialize me with an explanation of the error.
Method	trap	Trap this failure if its type is in a predetermined list.
Method	check	Check if this failure's type is in a predetermined list.
Method	raiseException	Undocumented
Method	throwExceptionIntoGenerator	Throw the original exception into the given generator, preserving traceback information if available.
Method	__repr__	Undocumented
Method	__str__	Undocumented
Method	__getstate__	Avoid pickling objects in the traceback.
Method	cleanFailure	Remove references to other objects, replacing them with strings.
Method	getTracebackObject	Get an object that represents this Failure's stack that can be passed to traceback.extract_tb.
Method	getErrorMessage	Get a string of the exception which caused this Failure.
Method	getBriefTraceback	Undocumented
Method	getTraceback	Undocumented
Method	printTraceback	Emulate Python's standard error reporting mechanism.
Method	printBriefTraceback	Print a traceback as densely as possible.
Method	printDetailedTraceback	Print a traceback with detailed locals and globals information.
Class Method	_findFailure	Find the failure that represents the exception currently in context.

value =

The exception instance responsible for this failure.

type =

The exception's class.

stack =

list of frames, innermost last, excluding Failure.__init__.

frames =

list of frames, innermost first.

def __init__(self, exc_value=None, exc_type=None, exc_tb=None, captureVars=False): (source)

Initialize me with an explanation of the error.

By default, this will use the current exception (sys.exc_info()). However, if you want to specify a particular kind of failure, you can pass an exception as an argument.

If no exc_value is passed, then an "original" Failure will be searched for. If the current exception handler that this Failure is being constructed in is handling an exception raised by raiseException, then this Failure will act like the original Failure.

For exc_tb only traceback instances or None are allowed. If None is supplied for exc_value, the value of exc_tb is ignored, otherwise if exc_tb is None, it will be found from execution context (ie, sys.exc_info).

Parameters captureVars if set, capture locals and globals of stack frames. This is pretty slow, and makes no difference unless you are going to use printDetailedTraceback.

def trap(self, *errorTypes): (source)

Trap this failure if its type is in a predetermined list.

This allows you to trap a Failure in an error callback. It will be automatically re-raised if it is not a type that you expect.

The reason for having this particular API is because it's very useful in Deferred errback chains:

   def _ebFoo(self, failure):
       r = failure.trap(Spam, Eggs)
       print 'The Failure is due to either Spam or Eggs!'
       if r == Spam:
           print 'Spam did it!'
       elif r == Eggs:
           print 'Eggs did it!'

If the failure is not a Spam or an Eggs, then the Failure will be 'passed on' to the next errback. In Python 2 the Failure will be raised; in Python 3 the underlying exception will be re-raised.

def check(self, *errorTypes): (source)

Check if this failure's type is in a predetermined list.

Returns the matching Exception type, or None if no match.

def raiseException(self): (source)

Undocumented

def throwExceptionIntoGenerator(self, g): (source)

overridden in twisted.spread.pb.CopiedFailure

Throw the original exception into the given generator, preserving traceback information if available.

Returns	The next value yielded from the generator.
Raises	StopIteration	If there are no more values in the generator.
	anything else	Anything that the generator raises.

@classmethod
def _findFailure(cls): (source)

Find the failure that represents the exception currently in context.

def __repr__(self): (source)

Undocumented

def __str__(self): (source)

Undocumented

def __getstate__(self): (source)

Avoid pickling objects in the traceback.

def cleanFailure(self): (source)

Remove references to other objects, replacing them with strings.

On Python 3, this will also set the __traceback__ attribute of the exception instance to None.

def getTracebackObject(self): (source)

Get an object that represents this Failure's stack that can be passed to traceback.extract_tb.

If the original traceback object is still present, return that. If this traceback object has been lost but we still have the information, return a fake traceback object (see _Traceback). If there is no traceback information at all, return None.

def getErrorMessage(self): (source)

Get a string of the exception which caused this Failure.

def getBriefTraceback(self): (source)

Undocumented

def getTraceback(self, elideFrameworkCode=0, detail='default'): (source)

Undocumented

def printTraceback(self, file=None, elideFrameworkCode=False, detail='default'): (source)

overridden in twisted.spread.pb.CopiedFailure

Emulate Python's standard error reporting mechanism.

Parameters	file	If specified, a file-like object to which to write the traceback.
	elideFrameworkCode	A flag indicating whether to attempt to remove uninteresting frames from within Twisted itself from the output.
	detail	A string indicating how much information to include in the traceback. Must be one of `'brief'`, `'default'`, or `'verbose'`.

t.p.f.Failure : class documentation