Redis: How to parse a list result

Question

I am storing a list in Redis like this:

redis.lpush('foo', [1,2,3,4,5,6,7,8,9])

And then I get the list back like this:

redis.lrange('foo', 0, -1)

and I get something like this:

[b'[1, 2, 3, 4, 5, 6, 7, 8, 9]']

How can I convert this to actual Python list?

Also, I don’t see anything defined in RESPONSE_CALLBACKS that can help? Am I missing something?

A possible solution (which in my opinion sucks) can be:

result = redis.lrange('foo',0, -1)[0].decode()

result = result.strip('[]')

result = result.split(', ')

# lastly, if you know all your items in the list are integers
result = [int(x) for x in result]

UPDATE

Ok, so I got the solution.

Actually, the lpush function expects all the list items be passed as arguments and NOT as a single list. The function signature from redis-py source makes it clear…

def lpush(self, name, *values):
    "Push ``values`` onto the head of the list ``name``"
    return self.execute_command('LPUSH', name, *values)

What I am doing above is send a single list as an argument, which is then sent to redis as a SINGLE item.

I should be unpacking the list instead as suggested in the answer:

redis.lpush('foo', *[1,2,3,4,5,6,7,8,9])

which returns the result I expect…

redis.lrange('foo', 0, -1)
[b'9', b'8', b'7', b'6', b'5', b'4', b'3', b'2', b'1']

Asked By: treecoder

||

Source

Answer 1

import json
r = [b'[1, 2, 3, 4, 5, 6, 7, 8, 9]']
rstr = r[0]
res_list = json.loads(rstr)

Answered By: Yarkee

Answer 2

I think you’re bumping into semantics which are similar to the distinction between list.append() and list.extend(). I know that this works for me:

myredis.lpush('foo', *[1,2,3,4])

… note the * (map-over) operator prefixing the list!

Answered By: Jim Dennis

Answer 3

Another way: you can use RedisWorks library.

pip install redisworks

>>> from redisworks import Root
>>> root = Root()
>>> root.foo = [1,2,3,4,5,6,7,8,9]  # saves it to Redis as a list
...
>>> print(root.foo)  # loads it from Redis later

It converts python types to Redis types and vice-versa. So even if you had nested list, it would have worked:

>>> root.sides = [10, [1, 2]]  # saves it as list in Redis.
>>> print(root.sides)  # loads it from Redis
[10, [1, 2]]
>>> type(root.sides[1])
<class 'list'>

Disclaimer: I wrote the library. Here is the code: https://github.com/seperman/redisworks

Answered By: Seperman

Redis: How to parse a list result

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