def reconstruct_message_list(message_list):
  """
  为了让多条消息能够以更结构化的方式返回给调用者，
  将 Redis 返回的多条消息从原来的格式：
  [(id1, {k1:v1, k2:v2, ...}), (id2, {k1:v1, k2:v2, ...}), ...]
  转换成以下格式：
  [{id1: {k1:v1, k2:v2, ...}}, {id2: {k1:v1, k2:v2, ...}}, ...]
  """  result = []
  for id, kvs in message_list:
    result.append({id: kvs})
  return result
def get_message_from_nested_list(lst):
  """
  从嵌套列表中取出消息本体。
  """
  return lst[0][1]
class MessageQueue:
  """
  使用 Redis 流实现的消息队列。
  """
  def __init__(self, client, stream_key):
    self.client = client
    self.stream = stream_key
  def add_message(self, key_value_pairs):
    """
    将给定的键值对存入到消息里面，并返回相应的消息 ID 。
    """
    return self.client.xadd(self.stream, key_value_pairs)
  def get_message(self, message_id):
    """
    根据给定的消息 ID 返回相应的消息，如果消息不存在则返回 None 。
    """
    reply = self.client.xrange(self.stream, message_id, message_id)
    if len(reply) == 1:
      return get_message_from_nested_list(reply)

  def remove_message(self, message_id):
    """
    根据给定的消息 ID 删除相应的消息，如果消息不存在则忽略该动作。
    """
    self.client.xdel(self.stream, message_id)

  def len(self):
    """
    返回消息队列的长度。
    """
    return self.client.xlen(self.stream)

  def get_by_range(self, start_id, end_id, max_item=10):
    """
    根据给定的 ID 区间范围返回队列中的消息。
    """
    reply = self.client.xrange(self.stream, start_id, end_id, max_item)
    return reconstruct_message_list(reply)

  def iterate(self, start_id=0, max_item=10):
    """
    对消息队列进行迭代，返回最多 N 条大于给定 ID 的消息。
    """
    reply = self.client.xread({self.stream: start_id}, max_item)
    if len(reply) == 0:
      return list()
    else:
      messages = get_message_from_nested_list(reply)
      return reconstruct_message_list(messages)

> from redis import Redis
> from message_queue import MessageQueue
> client = Redis(decode_responses=True)
> mq = MessageQueue(client, "mq")

> for i in range(10):
...  key = "key{0}".format(i)
...  value = "value{0}".format(i)
...  msg = {key:value}
...  mq.add_message(msg)
...
'1554113926280-0'
'1554113926280-1'
'1554113926281-0'
'1554113926281-1'
'1554113926281-2'
'1554113926281-3'
'1554113926281-4'
'1554113926281-5'
'1554113926281-6'
'1554113926282-0'

> mq.get_message('1554113926280-0')
{'key0': 'value0'}
> mq.get_message('1554113926280-1')
{'key1': 'value1'}
> mq.get_by_range("-", "+", 3)
[{'1554113926280-0': {'key0': 'value0'}}, {'1554113926280-1': {'key1': 'value1'}}, {'1554113926281-0': {'key2': 'value2'}}]

> mq.iterate(0, 3)
[{'1554113926280-0': {'key0': 'value0'}}, {'1554113926280-1': {'key1': 'value1'}}, {'1554113926281-0': {'key2': 'value2'}}]
> mq.iterate('1554113926281-0', 3)
[{'1554113926281-1': {'key3': 'value3'}}, {'1554113926281-2': {'key4': 'value4'}}, {'1554113926281-3': {'key5': 'value5'}}]