This is a model that implements (most of) the python dictionary interface. Meaning, you can work with this model exactly like a python dictionary, and it handles querying the database for it's values, saving/deleting the helper objects, etc.
I wrote this originally when I needed to store an arbitrary dictionary in the database, and decided to work it up into a near-complete implementation of a dictionary.
In order to make sure that the dictionary is the most optimized possible, I have a static method that can be used for retrieval. Feel free to ignore it if you don't care about optimizing database queries.
Here's an example:
Python 2.6.1 (r261:67515, Jun 24 2010, 21:47:49)
[GCC 4.2.1 (Apple Inc. build 5646)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> from binder.models import Dictionary
>>> d = Dictionary.getDict('Foobar')
>>> print d
{u'Foobar': u'omgbbq', u'HAHAHAH': u"who's afraid of a big, black, bat?"}
>>> d['pot'] = 'The kettle is black.'
>>> print d
{u'Foobar': u'omgbbq', u'pot': u'The kettle is black.', u'HAHAHAH': u"who's afraid of a big, black, bat?"}
>>> print d['pot']
The kettle is black.
>>> for k, v in d.iteritems():
... print k +":", v
...
Foobar: omgbbq
HAHAHAH: who's afraid of a big, black, bat?
pot: The kettle is black.
>>> print d.keys()
[u'Foobar', u'HAHAHAH', u'pot']
>>> print d.values()
[u'omgbbq', u"who's afraid of a big, black, bat?", u'The kettle is black.']
>>>
There's several more functions that I've implemented; check the code to see. (An interesting note: DictField saves immediately upon making a change, which is good to keep in mind in case that functionality isn't expected.)
Hope someone finds this useful. :)
--Chris
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class Dictionary(models.Model):
"""A model that represents a dictionary. This model implements most of the dictionary interface,
allowing it to be used like a python dictionary.
"""
name = models.CharField(max_length=255)
@staticmethod
def getDict(name):
"""Get the Dictionary of the given name.
"""
df = Dictionary.objects.select_related().get(name=name)
return df
def __getitem__(self, key):
"""Returns the value of the selected key.
"""
return self.keyvaluepair_set.get(key=key).value
def __setitem__(self, key, value):
"""Sets the value of the given key in the Dictionary.
"""
try:
kvp = self.keyvaluepair_set.get(key=key)
except KeyValuePair.DoesNotExist:
KeyValuePair.objects.create(container=self, key=key, value=value)
else:
kvp.value = value
kvp.save()
def __delitem__(self, key):
"""Removed the given key from the Dictionary.
"""
try:
kvp = self.keyvaluepair_set.get(key=key)
except KeyValuePair.DoesNotExist:
raise KeyError
else:
kvp.delete()
def __len__(self):
"""Returns the length of this Dictionary.
"""
return self.keyvaluepair_set.count()
def iterkeys(self):
"""Returns an iterator for the keys of this Dictionary.
"""
return iter(kvp.key for kvp in self.keyvaluepair_set.all())
def itervalues(self):
"""Returns an iterator for the keys of this Dictionary.
"""
return iter(kvp.value for kvp in self.keyvaluepair_set.all())
__iter__ = iterkeys
def iteritems(self):
"""Returns an iterator over the tuples of this Dictionary.
"""
return iter((kvp.key, kvp.value) for kvp in self.keyvaluepair_set.all())
def keys(self):
"""Returns all keys in this Dictionary as a list.
"""
return [kvp.key for kvp in self.keyvaluepair_set.all()]
def values(self):
"""Returns all values in this Dictionary as a list.
"""
return [kvp.value for kvp in self.keyvaluepair_set.all()]
def items(self):
"""Get a list of tuples of key, value for the items in this Dictionary.
This is modeled after dict.items().
"""
return [(kvp.key, kvp.value) for kvp in self.keyvaluepair_set.all()]
def get(self, key, default=None):
"""Gets the given key from the Dictionary. If the key does not exist, it
returns default.
"""
try:
return self[key]
except KeyError:
return default
def has_key(self, key):
"""Returns true if the Dictionary has the given key, false if not.
"""
return self.contains(key)
def contains(self, key):
"""Returns true if the Dictionary has the given key, false if not.
"""
try:
self.keyvaluepair_set.get(key=key)
return True
except KeyValuePair.DoesNotExist:
return False
def clear(self):
"""Deletes all keys in the Dictionary.
"""
self.keyvaluepair_set.all().delete()
def __unicode__(self):
"""Returns a unicode representation of the Dictionary.
"""
return unicode(self.asPyDict())
def asPyDict(self):
"""Get a python dictionary that represents this Dictionary object.
This object is read-only.
"""
fieldDict = dict()
for kvp in self.keyvaluepair_set.all():
fieldDict[kvp.key] = kvp.value
return fieldDict
class KeyValuePair(models.Model):
"""A Key-Value pair with a pointer to the Dictionary that owns it.
"""
container = models.ForeignKey(Dictionary, db_index=True)
key = models.CharField(max_length=240, db_index=True)
value = models.CharField(max_length=240, db_index=True)
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