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 with redis   For example  the following code does not work    Code that doesn t work r set  this dict   my dict     to store my dict in this dict r get  this dict      to retrieve my dict

User · Answer

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.

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

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

HGET => hget
HSET => hset
HMGET => hmget
HMSET => hmset
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.

User · Answer

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

User · Answer

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

User · Answer

If you want to store a python dict in redis  it is better to store it as json string   import redis  r   redis StrictRedis host  localhost   port 6379  db 0  mydict      var1    5   var2    9   var3    1  5  9    rval   json dumps mydict  r set  key1   rval    While retrieving de-serialize it using json loads  data   r get  key1   result   json loads data  arr   result  var3     What about types  eg bytes  that are not serialized by json functions    You can write encoder decoder functions for types that cannot be serialized by json functions  eg  writing base64 ascii encoder decoder function for byte array

User · Answer

You can do it by hmset  multiple keys can be set using hmset    hmset  RedisKey   dictionaryToSet   import redis conn   redis Redis  localhost    user     Name   Pradeep    Company   SCTL    Address   Mumbai    Location   RCP    conn hmset  pythonDict   user   conn hgetall  pythonDict      Company    SCTL    Address    Mumbai    Location    RCP    Name    Pradeep

User · Answer

HMSET is deprecated  You can now use HSET with a dictionary as follows   import redis r   redis Redis  localhost    key    hashexample   queue entry           version   1 2 3         tag   main         status   CREATED          timeout   30        r hset key None None queue entry

User · Answer

The redis SET command stores a string  not arbitrary data  You could try using the redis HSET command to store the dict as a redis hash with something like  for k v in my dict iteritems        r hset  my dict   k  v    but the redis datatypes and python datatypes don t quite line up  Python dicts can be arbitrarily nested  but a redis hash is going to require that your value is a string  Another approach you can take is to convert your python data to string and store that in redis  something like   r set  this dict   str my dict     and then when you get the string out you will need to parse it to recreate the python object

User · Answer

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

User · Answer

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      lt     this return an error as y is actually a string conn set  test  y   z eval conn get  test    print z  nome      lt     this really works    I did not test it for efficiency speed

User · Answer

Another way  you can use RedisWorks library   pip install redisworks   gt  gt  gt  from redisworks import Root  gt  gt  gt  root   Root    gt  gt  gt  root something    1  a    b    2  2      saves it as Hash type in Redis      gt  gt  gt  print root something     loads it from Redis   b    2  2   1   a    gt  gt  gt  root something  b   2  2   It converts python types to Redis types and vice-versa    gt  gt  gt  root sides    10   1  2      saves it as list in Redis   gt  gt  gt  print root sides     loads it from Redis  10   1  2    gt  gt  gt  type root sides 1    lt class  list  gt    Disclaimer  I wrote the library  Here is the code  https   github com seperman redisworks

User · Answer

you can pickle your dict and save as string   import pickle import redis  r   redis StrictRedis  localhost   mydict    1 2 2 3 3 4  p mydict   pickle dumps mydict  r set  mydict  p mydict   read dict   r get  mydict   yourdict   pickle loads read dict

[python] How to store and retrieve a dictionary with redis

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