Storing tracebacks

[George Sakkis]

I'm reading the docs on sys.exc_info() but I can't tell for sure
whether I'm using it safely to get a snapshot of an exception and
reraise it later. The use case is a class which acts like a deferred
callable, a callable that will be called at some point in the future
(possibly in a different thread) and whose result or raised exception
is to be stored as an attribute. This will be available by calling the
result() method, which returns the original result or reraises the
exception:

class JobRequest(object):

    def __init__(self, *args, **kwds):
        self.args = args
        self.kwds = kwds
        self._exc_info = None

    def __call__(self):
        raise NotImplementedError('Abstract method')

    def process(self):
        try:
            self._result = self(*self.args, **self.kwds)
        except:
            self._exc_info = sys.exc_info()
        else:
            self._exc_info = None

    def result(self):
        if self._exc_info is not None:
            type,exception,traceback = self._exc_info
            raise type,exception,traceback
        try: return self._result
        except AttributeError:
            raise UnprocessedRequestError()

class UnprocessedRequestError(RuntimeError):
    pass


So far it seems it works as expected but I'd like to know if this is
error-prone and why.

George