This is useful especially during the model-creation stage, when things are in constant flux. The `freshdb` command will drop the project's database, then create a new one. A common use case: manage.py freshdb manage.py syncdb
This fields.py file defines a new model field type, "JsonObjectField," which is designed to allow the storage of arbitrary Python objects in Django TextFields. It is intended primarily to allow the storage of Python dictionaries or list objects. As the name implies, it converts objects to JSON for storage; this conversion happens transparently, so from your model's perspective, the field stores and retrieves the actual objects.
*WARNING* This is *extremely* slow. This snippet allows you to easily prevent *most* race conditions (if used properly). Feel free to extend on top of this as you like, I'd appreciate any comments to [email protected]
This view assumes you have downloaded [modelviz.py](http://django-command-extensions.googlecode.com/svn/trunk/extensions/management/modelviz.py) and placed it in a python module called utils within my_project. You also must have graphviz installed and a subprocess-capable python. From there you can feed it a URL query list of the options you want to pass to generate_dot, and it will dynamically draw png or svg images of your model relationships right in the browser. All it wants is a nice form template for graphically selecting models. Most of this code and the main idea thereof was shamelessly plagiarized from [someone else](http://gundy.org/). Examples: `http://localhost:8000/model_graph/?image_type=svg&app_labels=my_app&include_models=Polls&include_models=Choices` `http://localhost:8000/model_graph/?image_type=png&all_applications&disable_fields&group_models`
Detect type of database (MySQL, PostgreSQL or SQLite) and make backup. In this moment ONLY WORK in GNU/Linux, NOT WIN.
Sometimes you just need to count things (or create unique-for-your-application IDs). This model class allows you to run as many persistent counters as you like. Basic usage looks like this: >>> Counter.next() 0 >>> Counter.next() 1L >>> Counter.next() 2L That uses the "default" counter. If you want to create and use a different counter, pass its name as a string as the parameter to the method: >>> Counter.next('hello') 0 >>> Counter.next('hey') 0 >>> Counter.next('hello') 1L >>> Counter.next('hey') 1L >>> Counter.next('hey') 2L You can also get the value as hex (if you want slightly shorter IDs, for use in URLs for example): >>> Counter.next_hex('some-counter-that-is-quite-high') 40e
This is an extension of the DecimalField database field that uses my [Currency Object](http://www.djangosnippets.org/snippets/1525/), [Currency Widget](http://www.djangosnippets.org/snippets/1526/), and [Currency Form Field](http://www.djangosnippets.org/snippets/1527/). I placed my Currency object in the Django\\utils directory, the widget in Django\\froms\\widgets_special.py, and the form field in Django\\forms\\fields_special.py because I integrated this set of currency objects into the Admin app ( [here](http://www.djangosnippets.org/snippets/1529/) ) and it was just easier to have everything within Django. UPDATE 08-18-2009: Added 'import decimal' and modified to_python slightly. The rest of the series: [Currency Object](http://www.djangosnippets.org/snippets/1525/), [Currency Widget](http://www.djangosnippets.org/snippets/1526/), [Currency Form Field](http://www.djangosnippets.org/snippets/1527/), [Admin Integration](http://www.djangosnippets.org/snippets/1529/)
I needed the ability to serialize and deserialize my database, which contains millions of objects. The existing XML serializer encountered spurious parse errors; the JSON serializer failed to handle UTF-8 even when it was asked to; and both the JSON and YAML serializers tried to keep all the representations in memory simultaneously. This custom serializer is the only one that has done the job. It uses YAML's "stream of documents" model so that it can successfully serialize and deserialize large databases.
This script generates an [GraphViz](http://www.graphviz.org/) graph of your database structure from your django models. See the usage if the file underneath the license.
Simple middelware that listens for redirect responses, store the request's query log in the session when it finds one, and starts the next request's log off with those queries from before the redirect.
There are a lot of reasons why you should not do this. But nevertheless it might be useful in certain situations. If your database does not change and you want to use validators etc you better use inspectdb from django-admin.py
First off: This snippet is more or less obsoleted by [snippet #259](/snippets/259/). The way that snippet #259 uses feels cleaner and more usable. It is basically the same code but the magic works a little bit different. In case you prefer this way, I've left this snippet as-is. Maybe you know this problem: you have some objects in your database and would like to display them in some way. The problem: the Django ORM does not provide any way to sort model instances by a user-defined criterion. There was already a plug-in in SQLAlchemy called [orderinglist](http://www.sqlalchemy.org/docs/plugins.html#plugins_orderinglist), so implementing this in Django was basically not a big deal. Usage is (due to use of meta-classes) quite simple. It is recommended to save this snippet into a separate file called `positional.py`. To use it, you only have to import `PositionalSortMixIn` from the `positional` module and inherit from it in your own, custom model (but *before* you inherit from `models.Model`, the order counts).
Out of the box, Django e-mail fields for both database models and forms only accept plain e-mail addresses. For example, `[email protected]` is accepted. On the other hand, full e-mail addresses which include a human-readable name, for example the following address fails validation in Django: Joe Hacker <[email protected]> This package adds support for validating full e-mail addresses. **Database model example** from django import models from full_email.models import FullEmailField class MyModel(models.Model): email = FullEmailField() **Forms example** from django import forms from full_email.formfields import FullEmailField class MyForm(forms.Form): email = FullEmailField(label='E-mail address') I maintain this code in a [GitHub gist](https://gist.github.com/1505228). It includes some unit tests as well.
When you want to save integers to the db, you usually have the choice between 16-, 32- and 64-bit Integers (also 8- and 24-bit for MySQL). If that doesn't fit your needs and you want to use your db-memory more efficient, this field might be handy to you. Imagine you have 3 numbers, but need only 10 bit to encode each (i.e. from 0 to 1000). Instead of creating 3 smallint-fields (48 bit), you can create one 'ByteSplitterField' which implements 3 'subfields' and automatically encodes them inside a 32 bit integer. You don't have to take care how each 10-bit chunk is encoded into the 32-bit integer, it's all handled by the field (see also field's description). Additionally, the Field offers opportunity to use decimal_places for each of your subfields. These are 'binary decimal places', meaning the integer-content is automatically divided by 2, 4, 8, etc. when you fetch the value from the field. You can also specify how values are rounded ('round' parameter) and what happens when you try to save a value out of range ('overflow' parameter) Not implemented (maybe in the future if I should need it sometime): * signed values. All values are positive right now! * real (10-based) decimal places (actually you could probably directly use DecimalFields here) * further space optimization, i.e. saving into CharField that's length can be chosen byte-wise
This example shows, how to use database views with django models. NewestArticle models contains 100 newest Articles. Remember, that NewestArticle model is read-only. Tested with mysql.