Python Containers and Simple Models for Redis
Redisco allows you to store objects in Redis. It is inspired by the Ruby library Ohm and its design and code are loosely based on Ohm and the Django ORM. It is built on top of redis-py. It includes container classes that allow easier access to Redis sets, lists, and sorted sets.
Redisco requires redis-py 2.0.0 so get it first.
pip install redis
Then install redisco.
pip install redisco
The documentation is available at : https://redisco.readthedocs.org
- v0.1
If you want something that is compatible with the original project developed by you should consider v0.1. It works.
- v0.2
If you are adventurous and want to try a version that is going closer to Ohm project you should consider v0.2. Warning, your indexing keys will be broken (if you are planning to migrate).
- master
Well, expect things to be broken. Really broken.
from redisco import models
class Person(models.Model):
name = models.Attribute(required=True)
created_at = models.DateTimeField(auto_now_add=True)
fave_colors = models.ListField(str)
>>> person = Person(name="Conchita")
>>> person.is_valid()
True
>>> person.save()
True
>>> conchita = Person.objects.filter(name='Conchita')[0]
>>> conchita.name
'Conchita'
>>> conchita.created_at
datetime.datetime(2010, 5, 24, 16, 0, 31, 954704)
- Attribute
- Stores unicode strings. If used for large bodies of text, turn indexing of this field off by setting indexed=False.
- IntegerField
- Stores an int. Ints are stringified using unicode() before saving to Redis.
- Counter
- An IntegerField that can only be accessed via Model.incr and Model.decr.
- DateTimeField
- Can store a DateTime object. Saved in the Redis store as a float.
- DateField
- Can store a Date object. Saved in Redis as a float.
- TimeDeltaField
- Can store a TimeDelta object. Saved in Redis as a float.
- FloatField
- Can store floats.
- BooleanField
- Can store bools. Saved in Redis as 1's and 0's.
- ReferenceField
- Can reference other redisco model.
- ListField
- Can store a list of unicode, int, float, as well as other redisco models.
- required
- If True, the attirbute cannot be None or empty. Strings are stripped to check if they are empty. Default is False.
- default
- Sets the default value of the attribute. Default is None.
- indexed
- If True, redisco will create index entries for the attribute. Indexes are used in filtering and ordering results of queries. For large bodies of strings, this should be set to False. Default is True.
- validator
- Set this to a callable that accepts two arguments -- the field name and the value of the attribute. The callable should return a list of tuples with the first item is the field name, and the second item is the error.
- unique
- The field must be unique. Default is False.
DateField and DateTimeField Options
- auto_now_add
- Automatically set the datetime/date field to now/today when the object is first created. Default is False.
- auto_now
- Automatically set the datetime/date field to now/today everytime the object is saved. Default is False.
You can specify some options in your Model to control the behaviour of the back scene.
class User(models.Model):
firstname = models.Attribute()
lastname = models.Attribute()
@property
def fullname(self):
return "%s %s" % (self.firstname, self.lastname)
class Meta:
indices = ['fullname']
db = redis.Redis(host="localhost", db="6666")
key = 'Account'
indices is used to add extra indices that will be saved in the model.
db object will be used instead of the global redisco redis_client
key will be used as the main key in the redis Hash (and sub objects)
instead of the class name.
Managers are attached to Model attributes by looking for a __attr_name__
class attribute. If not present, then it defaults to the lowercase attribute
name in the Model.
class User(models.Model):
firstname = models.Attribute()
lastname = models.Attribute()
active = models.BooleanField(default=True)
class History(models.managers.Manager):
pass
class ObjectsManager(models.managers.Manager):
__attr_name__ = "objects"
def get_model_set(self):
return super(User.ObjectsManager, self).\
get_model_set().filter(active=True)
To save an object, call its save method. This returns True on success (i.e. when the object is valid) and False otherwise.
Calling Model.is_valid will validate the attributes and lists. Model.is_valid is called when the instance is being saved. When there are invalid fields, Model.errors will hold the list of tuples containing the invalid fields and the reason for its invalidity. E.g. [('name', 'required'),('name', 'too short')]
Fields can be validated using the validator argument of the attribute. Just pass a callable that accepts two arguments -- the field name and the value of the attribute. The callable should return a list of errors.
Model.validate will also be called before saving the instance. Override it to validate instances not related to attributes.
def not_me(field_name, value):
if value == 'Me':
return ((field_name, 'it is me'),)
class Person(models.Model):
name = models.Attribute(required=True, validator=not_me)
age = models.IntegerField()
def validate(self):
if self.age and self.age < 21:
self._errors.append(('age', 'below 21'))
>>> person = Person(name='Me')
>>> person.is_valid()
False
>>> person.errors
[('name', 'it is me')]
Queries are executed using a manager, accessed via the objects class attribute.
Person.objects.all()
Person.objects.filter(name='Conchita')
Person.objects.filter(name='Conchita').first()
Person.objects.all().order('name')
Person.objects.filter(fave_colors='Red')
Redisco has a limited support for queries involving ranges -- it can only filter fields that are numeric, i.e. DateField, DateTimeField, IntegerField, and FloatField. The zfilter method of the manager is used for these queries.
Person.objects.zfilter(created_at__lt=datetime(2010, 4, 20, 5, 2, 0)) Person.objects.zfilter(created_at__gte=datetime(2010, 4, 20, 5, 2, 0)) Person.objects.zfilter(created_at__in=(datetime(2010, 4, 20, 5, 2, 0), datetime(2010, 5, 1)))
Redisco has three containers that roughly match Redis's supported data structures: lists, sets, sorted set. Anything done to the container is persisted to Redis.
- Sets
>>> from redisco.containers import Set >>> s = Set('myset') >>> s.add('apple') >>> s.add('orange') >>> s.add('bananas', 'tomatoes') >>> s.add(['blackberries', 'strawberries']) >>> s.members set(['apple', 'blackberries', 'strawberries', 'orange', 'tomatoes', 'bananas']) >>> s.remove('apple', 'orange') True set(['strawberries', 'bananas', 'tomatoes', 'blackberries']) >>> s.remove(['bananas', 'blackberries']) True >> s.members set(['strawberries', 'bananas', 'tomatoes']) >>> t = Set('nset') >>> t.add('kiwi') >>> t.add('guava') >>> t.members set(['kiwi', 'guava']) >>> s.update(t) >>> s.members set(['kiwi', 'orange', 'guava', 'apple'])
- Lists
>>> from redisco.containers import List >>> l = List('alpha') >>> l.append('a') >>> l.append(['b', 'c']) >>> l.append('d', 'e', 'f') >>> 'a' in l True >>> 'd' in l False >>> len(l) 6 >>> l.index('b') 1 >>> l.members ['a', 'b', 'c', 'd', 'e', 'f']
- Sorted Sets
>>> zset = SortedSet('zset') >>> zset.members ['d', 'a', 'b', 'c'] >>> 'e' in zset False >>> 'a' in zset True >>> zset.rank('d') 0 >>> zset.rank('b') 2 >>> zset[1] 'a' >>> zset.add({'f' : 200, 'e' : 201}) >>> zset.members ['d', 'a', 'b', 'c', 'f', 'e'] >>> zset.add('d', 99) >>> zset.members ['a', 'b', 'c', 'd', 'f', 'e']
- Dicts/Hashes
>>> h = cont.Hash('hkey') >>> len(h) 0 >>> h['name'] = "Richard Cypher" >>> h['real_name'] = "Richard Rahl" >>> h <Hash 'hkey' {'name': 'Richard Cypher', 'real_name': 'Richard Rahl'}> >>> h.dict {'name': 'Richard Cypher', 'real_name': 'Richard Rahl'}
Some methods of the Redis client that require the key as the first argument can be accessed from the container itself.
>>> l = List('mylist') >>> l.lrange(0, -1) 0 >>> l.rpush('b') >>> l.rpush('c') >>> l.lpush('a') >>> l.lrange(0, -1) ['a', 'b', 'c'] >>> h = Hash('hkey') >>> h.hset('name', 'Richard Rahl') >>> h <Hash 'hkey' {'name': 'Richard Rahl'}>
All models and containers use a global Redis client object to interact with the key-value storage. By default, it connects to localhost:6379, selecting db 0. If you wish to specify settings:
import redisco redisco.connection_setup(host='localhost', port=6380, db=10)
The arguments to connect are simply passed to the redis.Redis init method.
For the containers, you can specify a second argument as the Redis client. That client object will be used instead of the default.
>>> import redis >>> r = redis.Redis(host='localhost', port=6381) >>> Set('someset', r)
Redisco uses nose for testing.
Install nosetests:
$ pip install nose
And test:
$ nosetests
Most of the concepts are taken from Soveran's Redis related Ruby libraries. cyx for sharing his expertise in indexing in Redis. Django, of course, for the popular model API.