django-metadata 0.1.4

Attach metadata to any Django models using redis

Attach metadata to any Django models using redis.

Installation

Either check out the package from GitHub or it pull from a release via PyPI:

pip install django-metadata

Usage

With django-metadata you can attach metadata to any Django models, you will be able to link keys and theirs values to any instances.

Currently only Redis is supported with only redis-py as backend.

Let’s say you have this model:

# models.py

from django.db import models

class User(models.Model):
    username = models.CharField(max_length=150)

Now you have to attach the MetadataMixin to your model:

# models.py

from django.db import models

from metadata.mixins import MetadataMixin

class User(MetadataMixin, models.Model):
    username = models.CharField(max_length=150)

You can customize the way django-metadata is storing your values by providing a metadata_key property to your model:

# models.py

from django.db import models

from metadata.mixins import MetadataMixin

class User(MetadataMixin, models.Model):
    username = models.CharField(max_length=150)

    def metadata_key(self):
        return 'metadata:utilisateur:%d' % self.pk

By default, the schema will be metadata:%(lowerclassname)s:%(primary_key)s.

Now we have connected our model to the mixin we can play with the API.

The API of MetadataContainer follows the same principes as dict.

Adding keys

>>> from myapp.models import User
>>> user = User.objects.create(username='thoas')
>>> user.metadata['mail_signup_sent'] = 1
>>> user = User.objects.get(username='thoas')
>>> user.metadata['mail_signup_sent']
1
>>> user.metadata = {'mail_signup_sent': 0}
>>> user.metadata['mail_signup_sent']
0

Removing keys

You can either removing a key by setting its value to None or use the del operator.

>>> del user.metadata['key']
>>> user.metadata['key']
Traceback (most recent call last):
    ...
KeyError: 'key'
>>> user.metadata.get('key', None)
None
>>> user.metadata['foo'] = 'bar'
>>> user.metadata['foo'] = None
>>> user.metadata['foo']
Traceback (most recent call last):
    ...
KeyError: 'foo'
>>> user.metadata.get('foo', None)
None
>>> user.metadata['key'] = 'value'
>>> user.metadata['foo'] = 'bar'
>>> user.metadata = {'foo': None}
>>> user.metadata['foo']
Traceback (most recent call last):
    ...
KeyError: 'foo'
>>> user.metadata['key']
value

Iterating keys

>>> 'value' in user.metadata
True
>>> user.metadata.values()
['value']
>>> user.metadata.keys()
['key']
>>> user.metadata.items()
[('key', 'value')]

Incrementing keys

As we are using Redis as storing engine you can use some of its nice features:

>>> user.metadata.incr('counter')
>>> user.metadata['counter']
1
>>> user.metadata.incr('counter', 2)
>>> user.metadata['counter']
3

Inspiration

django-metadata comes from an original idea of twidi.