gistfile1.py

class StepsProcessor(object):
    def __init__(self, steps, filename):
        self.steps = steps
        self.filename = filename

    def process(self):
        for i, step in self.enumerate_steps_to_process():
            try:
                self.process_step(step)
            except Exception:
                self.report_exception_on_step(step)

    def report_exception_on_step(self, step):
        traceback.print_exc()
        print 'Exception occured on step #%s, "%s".' % (
            self.get_id_by_step(step), self.get_step_name(step)
        )
        next_step = self.get_next_step_by_step(step)
        print 'Next step is #%s, "%s."' % (
            self.get_id_by_step(next_step), self.get_step_name(step)
        )
        sys.exit()

    def get_steps_to_process(self):
        return self.steps[self.get_first_step_to_process():]

    def enumerate_steps_to_process(self):
        return enumerate(self.get_steps_to_process())

    def get_first_step_to_process(self):
        step = self.get_saved_step_id()
        if not step:
            return 0
        elif self.is_user_agreed_to_resume_from_step(step):
            return step
        else:
            return 0

    def is_user_agreed_to_resume_from_step(self, step):
        while True:
            try:
                return asbool(raw_input('Resume from step %s?: ' % self.get_id_by_step(step)))
            except ValueError:
                pass

    def process_step(self, step):
        self.save_step_to_state(step)
        step()

    def save_step_to_state(self, step):
        self.save_step_id(self.get_id_by_step(step))

    def get_next_step_by_step(self, step):
        next_step_id = self.get_id_by_step(step) + 1
        return self.get_step_by_id(next_step_id)

    def get_id_by_step(self, step):
        return self.steps.index(step)

    def get_step_by_id(self, step_id):
        return self.steps[step_id]

    def get_step_name(self, step):
        if isinstance(step, functools.partial):
            return step.func.__name__
        return step.__name__

    def save_step_id(self, step_id):
        with self.open_state_file() as state_file:
            state_file.write(str(step_id))

    def get_saved_step_id(self):
        with self.open_state_file() as state_file:
            try:
                return int(state_file.read())
            except (IOError, ValueError):
                return None

    def open_state_file(self):
        return open(self.filename, 'wb')