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Tag "model"

137 snippets

Snippet List

Binding signals to abstract models

Intro ----- I found a question on SO for which Justin Lilly's answer was correct but not as thorough as I'd like, so I ended up working on a simple snippet that shows how to bind signals at runtime, which is nifty when you want to bind signals to an abstract class. Bonus: simple cache invalidation! Question -------- [How do I use Django signals with an abstract model?](http://stackoverflow.com/questions/2692551/how-do-i-use-django-signals-with-an-abstract-model) I have an abstract model that keeps an on-disk cache. When I delete the model, I need it to delete the cache. I want this to happen for every derived model as well. If I connect the signal specifying the abstract model, this does not propagate to the derived models: pre_delete.connect(clear_cache, sender=MyAbstractModel, weak=False) If I try to connect the signal in an init, where I can get the derived class name, it works, but I'm afraid it will attempt to clear the cache as many times as I've initialized a derived model, not just once. Where should I connect the signal? Answer ------ I've created a custom manager that binds a post_save signal to every child of a class, be it abstract or not. This is a one-off, poorly tested code, so beware! It works so far, though. In this example, we allow an abstract model to define CachedModelManager as a manager, which then extends basic caching functionality to the model and its children. It allows you to define a list of volatile keys that should be deleted upon every save (hence the post_save signal) and adds a couple of helper functions to generate cache keys, as well as retrieving, setting and deleting keys. This of course assumes you have a cache backend setup and working properly.

  • managers
  • models
  • cache
  • model
  • manager
  • signals
  • abstract
  • signal
  • contribute_to_class
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Add custom fields to the built-in Group model

Add fields and extend Django's built-in `Group` model using a `OneToOneField` (i.e. a profile model). In this example, we add a `UUIDField`. Whenever a new group is created, we automatically (via signals) create a corresponding `Role` record referencing the newly created group. Whenever a Group is deleted, the corresponding Role is deleted as well.

  • model
  • group
  • uuid
  • signals
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PositionField

**This is a model field for managing user-specified positions.** Usage ===== Add a `PositionField` to your model; that's just about it. If you want to work with all instances of the model as a single collection, there's nothing else required. In order to create collections based on another field in the model (a `ForeignKey`, for example), set `unique_for_field` to the name of the field. It's probably also a good idea to wrap the `save` method of your model in a transaction since it will trigger another query to reorder the other members of the collection. Here's a simple example: from django.db import models, transaction from positions.fields import PositionField class List(models.Model): name = models.CharField(max_length=50) class Item(models.Model): list = models.ForeignKey(List, db_index=True) name = models.CharField(max_length=50) position = PositionField(unique_for_field='list') # not required, but probably a good idea save = transaction.commit_on_success(models.Model.save) Indices ------- In general, the value assigned to a `PositionField` will be handled like a list index, to include negative values. Setting the position to `-2` will cause the item to be moved to the second position from the end of the collection -- unless, of course, the collection has fewer than two elements. Behavior varies from standard list indices when values greater than or less than the maximum or minimum positions are used. In those cases, the value is handled as being the same as the maximum or minimum position, respectively. `None` is also a special case that will cause an item to be moved to the last position in its collection. Limitations =========== * Unique constraints can't be applied to `PositionField` because they break the ability to update other items in a collection all at once. This one was a bit painful, because setting the constraint is probably the right thing to do from a database consistency perspective, but the overhead in additional queries was too much to bear. * After a position has been updated, other members of the collection are updated using a single SQL `UPDATE` statement, this means the `save` method of the other instances won't be called. More === More information, including an example app and tests, is available on [Google Code](http://code.google.com/p/django-positions/).

  • lists
  • models
  • fields
  • model
  • field
  • list
  • sorting
  • ordering
  • collection
  • collections
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Multiple Choice model field

Usually you want to store multiple choices as a manytomany link to another table. Sometimes however it is useful to store them in the model itself. This field implements a model field and an accompanying formfield to store multiple choices as a comma-separated list of values, using the normal CHOICES attribute. You'll need to set maxlength long enough to cope with the maximum number of choices, plus a comma for each. The normal get_FOO_display() method returns a comma-delimited string of the expanded values of the selected choices. The formfield takes an optional max_choices parameter to validate a maximum number of choices.

  • multiple
  • model
  • form
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Django Dictionary Model

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

  • model
  • python
  • dict
  • dictionary
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CNPJ and CPF Validation for Models

The code was placed inside a helper file without using a class. The Django validator was not designed to work with validator classes, it would appear, so retrieving the value from the field proved to be a hassle. Just create a helper file, import it on your model, and use the validator in the standard way, as such: cnpj = models.CharField(unique=True, max_length=14, validators=[validate_CNPJ]) cpf = models.CharField(unique=True, max_length=14, validators=[validate_CPF])

  • model
  • validation
  • cnpj
  • cpf
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Password Validation - Require Letters and Numbers - no regex

Simple password validation for user registration - requires that password be 7 or more characters and contain both letters and numbers. Original validation with regex approach developed by kurtis. Optimized no-regex version based on code from watchedman ran as fast or significantly faster on all systems on which we tested it.

  • registration
  • model
  • regex
  • user
  • validation
  • form
  • password
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ISBN model field: displays 10- and 13-digit variants and external links

Requires [PyISBN](http://pypi.python.org/pypi/pyisbn/0.5.2). Use like so: class Book(models.Model): title = models.TextField() isbn = ISBNField() ... the link in the widget can be changed to amazon, borders, you name it. If the DB version is a 13-digit ISBN, the display box contains the 10-digit, labeled; and vice-versa.

  • django
  • model
  • python
  • widget
  • modelfield
  • isbn
  • books
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another UserForeignKey

This is another foreign key to User model. User is automatically associated before save. Requires: [ThreadlocalsMiddleware](http://code.djangoproject.com/wiki/CookBookThreadlocalsAndUser) Inspired by: [snippet 509](http://www.djangosnippets.org/snippets/509/)

  • foreignkey
  • model
  • user
  • field
  • users
  • user-foreign-key
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Model merging function

Generic function to merge model instances. Useful when you need to merge duplicate models together, e.g. for users. Based on http://djangosnippets.org/snippets/382/, with several enhancements: * *Type checking*: only Model subclasses can be used and testing that all instances are of same model class * *Handles symmetrical many-to-may*: original snippet failed in that case * *Filling up blank attrs of original when duplicate has it filled* * *Prepared to use outside of command-line*

  • django
  • model
  • generic
  • related
  • merge
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