twisted.python.failure.Failure class documentation

Part of twisted.python.failure View Source (View In Hierarchy)

Known subclasses: twisted.spread.pb.CopiedFailure, twisted.spread.pb.CopyableFailure

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).

ParameterscaptureVarsif 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.

Returnsthe 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.

ReturnsThe next value yielded from the generator.
RaisesStopIterationIf there are no more values in the generator.
anything elseAnything 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.

ParametersfileIf specified, a file-like object to which to write the traceback.
elideFrameworkCodeA flag indicating whether to attempt to remove uninteresting frames from within Twisted itself from the output.
detailA string indicating how much information to include in the traceback. Must be one of 'brief', 'default', or 'verbose'.
def printBriefTraceback(self, file=None, elideFrameworkCode=0): (source)

Print a traceback as densely as possible.

def printDetailedTraceback(self, file=None, elideFrameworkCode=0): (source)

Print a traceback with detailed locals and globals information.

API Documentation for Twisted, generated by pydoctor at 2017-06-11 10:59:01.