Dynamic on_enter/exit_* methods about transitions HOT 6 CLOSED

def __getattr__(self, name):
        if name.startswith('__'):
            if name in self.__dict__:
                return self.__dict__[name]
            else:
                raise AttributeError("{} does not exist".format(name))
        terms = name.split('_')
        if terms[0] in ['before', 'after']:
            name = '_'.join(terms[1:])
            if name not in self.events:
                raise MachineError('Event "%s" is not registered.' % name)
            return partial(self.events[name].add_callback, terms[0])

        # that's where the magic happens
        # on_enter / on_exit queries are concatenated with the current state 
        # and predefined with partial
        elif name.startswith('on_enter') or name.startswith('on_exit'):
            state = self.get_state('_'.join(terms[2:]))
            return partial(state.add_callback, terms[1])
        else:
            if name in self.__dict__:
                return self.__dict__[name]
            else:
                raise AttributeError("{} does not exist".format(name))

machine.on_exit_solid('say_goodbye')

#  Add enter/exit callbacks if there are existing bound methods
    enter_callback = 'on_enter_' + state_name
    if hasattr(self.model, enter_callback) and \
               inspect.ismethod(getattr(self.model, enter_callback)):
        state.add_callback('enter', enter_callback)
    exit_callback = 'on_exit_' + state_name
    if hasattr(self.model, exit_callback) and \
               inspect.ismethod(getattr(self.model, exit_callback)):
        state.add_callback('exit', exit_callback)