将数组追加到可能不存在的字典键

Question

for answer in answers:
    try:
        dic[answer.question_id] += [answer.rating]
    except KeyError:
        dic[answer.question_id] = [answer.rating]

我也可以这样做：

dic[answer.question_id] += [answer.rating] if dic[answer.question_id] else [answer.rating]

有没有更好的方法来完成相同的任务？非常感谢。