How to store and retrieve a dictionary with redis

Question

# I have the dictionary my_dict
my_dict = {
    \'var1\' : 5
    \'var2\' : 9
}
r = redis.StrictRedis()

How would I store my_dict and retrieve it w

Answer 1

If you don't know exactly how to organize data in Redis, I did some performance tests, including the results parsing. The dictonary I used (d) had 437.084 keys (md5 format), and the values of this form:

{"path": "G:\tests\2687.3575.json",
 "info": {"f": "foo", "b": "bar"},
 "score": 2.5}

First Test (inserting data into a redis key-value mapping):

conn.hmset('my_dict', d)  # 437.084 keys added in 8.98s

conn.info()['used_memory_human']  # 166.94 Mb

for key in d:
    json.loads(conn.hget('my_dict', key).decode('utf-8').replace("'", '"'))
    #  41.1 s

import ast
for key in d:
    ast.literal_eval(conn.hget('my_dict', key).decode('utf-8'))
    #  1min 3s

conn.delete('my_dict')  # 526 ms

Second Test (inserting data directly into Redis keys):

for key in d:
    conn.hmset(key, d[key])  # 437.084 keys added in 1min 20s

conn.info()['used_memory_human']  # 326.22 Mb

for key in d:
    json.loads(conn.hgetall(key)[b'info'].decode('utf-8').replace("'", '"'))
    #  1min 11s

for key in d:
    conn.delete(key)
    #  37.3s

As you can see, in the second test, only 'info' values have to be parsed, because the hgetall(key) already returns a dict, but not a nested one.

And of course, the best example of using Redis as python's dicts, is the First Test

Answer 2

One might consider using MessagePack which is endorsed by redis.

import msgpack

data = {
    'one': 'one',
    'two': 2,
    'three': [1, 2, 3]
}

await redis.set('my-key', msgpack.packb(data))
val = await redis.get('my-key')
print(msgpack.unpackb(val))

# {'one': 'one', 'two': 2, 'three': [1, 2, 3]}

Using msgpack-python and aioredis

Answer 3

As the basic answer has already give by other people, I would like to add some to it.

Following are the commands in REDIS to perform basic operations with HashMap/Dictionary/Mapping type values.

1. HGET => Returns value for single key passed
2. HSET => set/updates value for the single key
3. HMGET => Returns value for single/multiple keys passed
4. HMSET => set/updates values for the multiple key
5. HGETALL => Returns all the (key, value) pairs in the mapping.

Following are their respective methods in redis-py library :-

1. HGET => hget
2. HSET => hset
3. HMGET => hmget
4. HMSET => hmset
5. HGETALL => hgetall

All of the above setter methods creates the mapping, if it doesn't exists. All of the above getter methods doesn't raise error/exceptions, if mapping/key in mapping doesn't exists.

Example:
=======
In [98]: import redis
In [99]: conn = redis.Redis('localhost')

In [100]: user = {"Name":"Pradeep", "Company":"SCTL", "Address":"Mumbai", "Location":"RCP"}

In [101]: con.hmset("pythonDict", {"Location": "Ahmedabad"})
Out[101]: True

In [102]: con.hgetall("pythonDict")
Out[102]:
{b'Address': b'Mumbai',
 b'Company': b'SCTL',
 b'Last Name': b'Rajpurohit',
 b'Location': b'Ahmedabad',
 b'Name': b'Mangu Singh'}

In [103]: con.hmset("pythonDict", {"Location": "Ahmedabad", "Company": ["A/C Pri
     ...: sm", "ECW", "Musikaar"]})
Out[103]: True

In [104]: con.hgetall("pythonDict")
Out[104]:
{b'Address': b'Mumbai',
 b'Company': b"['A/C Prism', 'ECW', 'Musikaar']",
 b'Last Name': b'Rajpurohit',
 b'Location': b'Ahmedabad',
 b'Name': b'Mangu Singh'}

In [105]: con.hget("pythonDict", "Name")
Out[105]: b'Mangu Singh'

In [106]: con.hmget("pythonDict", "Name", "Location")
Out[106]: [b'Mangu Singh', b'Ahmedabad']

I hope, it makes things more clear.

Answer 4

An other way you can approach the matter:

import redis
conn = redis.Redis('localhost')

v={'class':'user','grants': 0, 'nome': 'Roberto', 'cognome': 'Brunialti'}

y=str(v)
print(y['nome']) #<=== this return an error as y is actually a string
conn.set('test',y)

z=eval(conn.get('test'))
print(z['nome']) #<=== this really works!

I did not test it for efficiency/speed.

Answer 5

Try rejson-py which is relatively new since 2017. Look at this introduction.

from rejson import Client, Path

rj = Client(host='localhost', port=6379)

# Set the key `obj` to some object
obj = {
    'answer': 42,
    'arr': [None, True, 3.14],
    'truth': {
        'coord': 'out there'
    }
}
rj.jsonset('obj', Path.rootPath(), obj)

# Get something
print 'Is there anybody... {}?'.format(
    rj.jsonget('obj', Path('.truth.coord'))
)

# Delete something (or perhaps nothing), append something and pop it
rj.jsondel('obj', Path('.arr[0]'))
rj.jsonarrappend('obj', Path('.arr'), 'something')
print '{} popped!'.format(rj.jsonarrpop('obj', Path('.arr')))

# Update something else
rj.jsonset('obj', Path('.answer'), 2.17)