Django KVModel

KVModel provides a very convenient way to create key-value models with just two lines of code.

from kvmodel.models import KVModel

class SystemSettings(KVModel):
    """
    SystemSettings Model now extends KVModel, and you will
    be able to access the key and the value fields on that Model
    """

Installation

You can Install django-kvmodel from PyPI.

pip install django-kvmodel

Configuration

Add kvmodel to your INSTALLED_APPS setting::

INSTALLED_APPS = (
    ...
    'kvmodel',
    ...
)

This will enable kvmodel, form more advanced settings please check the advanced section.

Usage

KVModel is an abstract model that has two fields key and value.

• key is a unique CharField.
• value is a SerializableField which means that it's type is restored when loading an instance from the database, check out the advanced section for more details about SerializableField.

Defining key-value models

Extend KVModel to create a key-value model:

from kvmodel.models import KVModel

class Settings(KVModel):
    pass

Creating instances

You can create Instances the same way you will use a Django Model

setting = Settings(key='dragons_in_store', value=123)

for a persistent instance

setting = Settings.create(key='dragons_in_store', value=123)

Retrieving instances

you can use Django filters to retrieve data from your model, however you shouldn't use the value field to search for data.

there is also a method to retrieve objects using their key:

setting = Settings.get_by_key('dragons_in_store')

which is equivalent to:

setting = Settings.get(key='dragons_in_store')

Advanced Usage

SerializableField

this is a custom field that extends TextField, it encodes the data before saving and decodes it once an instance is loaded from the database.

you can use SerilizableField like this:

from kvmodes.models import KVModel
from kvmodel.fields import SerilizableField

class SystemSettings(KVModel):
    default = SerialiableField()

By default SerializableField uses JSON for de-serializing data however you can define your custom de-serializers.

the serialize function is called before the object is saved to the database, it should accept the value and returns a string.

the deserialize function is called when loading an instance from the data base, it should accept a string and return the restored value

Defining Custom serializer/derserilizer

define the functions you want to use as de-serilizers:

aes_serialize(value):
    return aes_encrypt(json.dumps(value), key='super secret key')

aes_deserialize(s):
    return json.loads(aes_decrypt(s, key='super secret key'))

next you should update the KVMODEL setting:

KVMODEL = {
    'SERIALIZE_FUNCTION': 'appname.modulename.aes_serilize',
    'DESERIALIZE_FUNCTION': 'appname.modulename.aes_deserialize'
}