how to store a complex object in redis (using redis-py)

You can't create nested structures in Redis, meaning you can't (for example) store a native redis list inside a native redis hash-map.

If you really need nested structures, you might want to just store a JSON-blob (or something similar) instead. Another option is to store an "id"/key to a different redis object as the value of the map key, but that requires multiple calls to the server to get the full object.

Actually, you can store python objects in redis using the built-in module pickle.

Here is example.

import pickle
import redis

r = redis.StrictRedis(host='localhost', port=6379, db=0)
obj = ExampleObject()
pickled_object = pickle.dumps(obj)
r.set('some_key', pickled_object)
unpacked_object = pickle.loads(r.get('some_key'))
obj == unpacked_object

If your data is JSON-serializable, then that may be the better option than saving python pickles to an external database, since it's a more common standard outside of Python, is more human-readable on its own, and avoids a rather large attack vector.

JSON Example:

import json
import redis

r = redis.StrictRedis(host='localhost', port=6379, db=0)

images= [
    {'type':'big', 'url':'....'},
    {'type':'big', 'url':'....'},
    {'type':'big', 'url':'....'},
]

# Convert python dict to JSON str and save to Redis
json_images = json.dumps(images)
r.set('images', json_images)

# Read saved JSON str from Redis and unpack into python dict
unpacked_images = json.loads(r.get('images'))
images == unpacked_images

python 3:

unpacked_images = json.loads(r.get('images').decode('utf-8'))
images == unpacked_images