以下代码效果很好:

next_movie = Movies.query(Movies.added < movie.added)
next_movie = next_movie.order(-Movies.added)
next_movie = next_movie.get(keys_only = True)
if next_movie:
    next_url = next_movie.id()
else:
    next_url = ''

prev_movie = Movies.query(Movies.added > movie.added)
prev_movie = prev_movie.order(Movies.added)
prev_movie = prev_movie.get(keys_only = True)
if prev_movie:
    prev_url = prev_movie.id()
else:
    prev_url = ''
return next_url, prev_url