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Tag "model"

137 snippets

Snippet List

update_or_create

Django provides a `get_or_create` helper method in the `models.Manager` class which looks up an object for the given `kwargs`, creating one if necessary. But sometime you need a method which updates the object with given `kwargs` or creates it if it's not found. This snippet provides the helper for that purpose. Use the snippet like this: from django.db import models class PersonManager(models.Manager): update_or_create = _update_or_create class Person(models.Model): first_name = models.CharField() last_name = models.CharField() city = models.CharField() objects = PersonManager() person, created, updated = Person.objects.update_or_create(first_name="John", last_name="Smith", defaults=dict(city="London")) The method returns a tuple of (`object`, `created`, `updated`), where `created` and `updated` are booleans specifying whether an `object` was created or updated respectively. Both `created` and `updated` are `false` if `object` is neither created nor updated (that is `object` has just been fetched "as is" from db). This happens if the update fails.

  • model
  • helper
  • update
  • create
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Enumeration field

These three classes allows you to use enumerations (choices) in more natural model-like style. You haven't to use any magic numbers to set/get field value. And if you would like to make your enumeration a full-fledged django-model, migration should be easy. Note, that you can subclass Item to add some context-specific attributes to it, such as `get_absolute_url()` method for instance. Examples are provided in the form of `doctest` in the second half of the snippet.

  • newforms
  • choice
  • model
  • field
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Model manager with row caching

RowCacheManager is a model manager that will try to fetch any 'get' (i.e., single-row) requests from the cache. ModelWithCaching is an abstract base model that does some extra work that you'll probably want if you're using the RowCacheManager. So to use this code, you just need to do two things: First, set objects=RowCacheManager() in your model definition, then inherit from ModelWithCaching if you want the invalidation for free. If you are unusually brave, use the metaclass for ModelWithCaching and you won't even need the "objects=RowCacheManager()" line.

  • get
  • model
  • manager
  • model-inheritance
  • caching
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Django Model Inheritance

This snippet shows an alternative and interesting way to do Model Inheritance in Django. For description of the code, follow the inline comments.

  • model
  • inheritance
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MarkupTextField

I updated [MarkdownTextField](http://www.djangosnippets.org/snippets/882/) to have some choices in markup. It currently support for Markdown, Textile, Plain Text, and Plain HTML. It will add `%s_html` for the complied HTML and `%s_markup_choices` for a drop down of markup choices. Usage: class MyModel(models.Model): description = MarkupTextField()

  • model
  • markup
  • markdown
  • textile
  • field
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ParentModel and ChildManager for Model Inheritance

This is the approach I've taken to access instances of child models from their parent. Functionally it's very similar to snippets [1031](http://www.djangosnippets.org/snippets/1031/) and [1034](http://www.djangosnippets.org/snippets/1034/), but without the use of `django.contrib.contenttypes`. Usage: class Post(ParentModel): title = models.CharField(max_length=50) objects = models.Manager() children = ChildManager() def __unicode__(self): return self.title def get_parent_model(self): return Post class Article(Post): text = models.TextField() class Photo(Post): image = models.ImageField(upload_to='photos/') class Link(Post): url = models.URLField() In this case, the `Post.children` manager will return a queryset containing instances of the appropriate child model, rather than instances of `Post`. >>> Post.objects.all() [<Post: Django>, <Post: Make a Tumblelog>, <Post: Self Portrait>] >>> Post.children.all() [<Link: Django>, <Article: Make a Tumblelog>, <Photo: Self Portrait>]

  • model
  • manager
  • queryset
  • inheritance
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duplicate model object merging script

Use this function to merge model objects (i.e. Users, Organizations, Polls, Etc.) and migrate all of the related fields from the alias objects the primary object. Usage: from django.contrib.auth.models import User primary_user = User.objects.get(email='[email protected]') duplicate_user = User.objects.get(email='[email protected]') merge_model_objects(primary_user, duplicate_user)

  • django
  • fields
  • model
  • generic
  • related
  • merge
  • duplicates
  • genericforeignkey
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Markup Selection in Admin

This method lets you define your markup language and then processes your entries and puts the HTML output in another field on your database. I came from a content management system that worked like this and to me it makes sense. Your system doesn't have to process your entry every time it has to display it. You would just call the "*_html" field in your template. Requires: Django .96 [Markdown](http://cheeseshop.python.org/pypi/Markdown/1.6 "Python Package Index: Markdown") [Textile](http://cheeseshop.python.org/pypi/textile "Python Package Index: Textile")

  • admin
  • model
  • markup
  • markdown
  • textile
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Subclassing a model.field for newforms

The newforms fields are more capable than the django models fields. In this snippet, we subclass models.IntegerField, and add min_value and max_value. e.g. age = MMIntegerField('How old are you?', min_value=13, max_value=120)

  • newforms
  • fields
  • model
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Easier chainability with custom QuerySets

Django allows you to specify your own ModelManager with custom methods. However, these methods are chainable. That is, if you have a method on your PersonManager caled men(), you can't do this: Person.objects.filter(birth_date__year=1978).men() Normally, this isn't a problem, however your app may be written to take advantage of the chainability of querysets. For example, you may have an API method which may return a filtered queryset. You would want to call with_counts() on an already filtered queryset. In order to overcome this, we want to override django's QuerySet class, and then make the Manager use this custom class. The only downside is that your functions will not be implemented on the manager itself, so you'd have to call `Person.objects.all().men()` instead of `Person.objects.men()`. To get around this you must also implement the methods on the Manager, which in turn call the custom QuerySet method.

  • model
  • manager
  • queryset
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SearchableManager

A drop-in chainable manager for providing models with basic search features such as +/- modifiers, quoted exact phrases and ordering by relevance.

  • search
  • model
  • manager
  • queryset
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Clear nullable foreign keys on delete

Django 1.0 is apparently hard-coded for cascading deletes. I find that I often have nullable foreign keys on models whose records must not be deleted along with those they refer to. I override Model.delete() in an intermediate base class and execute this method to clear out all nullable foreign keys before allowing a delete to proceed.

  • model
  • delete
  • cascade
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Model Forms: Clean unique field

Often I want fields in my models to be unique - Django's `unique` works too late in model form validation and will throw an exception unless you check for it by hand. This is a bit of code that cleans up the boiler plate of checking if different fields are unique. Set `exclude_initial` to `False` if you want to raise an error if the unique field cannot be set to whatever value the instance had before. **Update** Thanks fnl for rightly pointing out that Django's `unique=True` does check for this - just make sure to pass `instance=obj` when you're initializing your forms. _HOWEVER_ a problem you'll typically run into with this is though you want a field to unique, you also want multiple entries to be able to be `blank`. This can help you!

  • forms
  • model
  • unique
  • model-forms
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