a template tag to invoke a method on an object with a variable

The django templating language is quite nice, and specifically limited to guide people in to making their business logic in the view, not in the template itself. Sometimes it can be difficult to do certain things in the template even though it seems like the most appropriate place to do this. I have an application that is heavily influenced by the user that is logged in in several ways. For example let us say I have a list of forums. Each forum has several discussions full of posts. This system of forums and discussions has permissions such that some users can not see some entities. Now, I can produce in the view the query set of what forums a user is allowed to see, and I want this list to display the latest post in each of those forums, but I have to restrict that to the posts that they can see. Easy enough, I have a method on the Forum object that takes a user object and does the appropriate filter to return the latest post that the user can see. The trick is the template is passed the query set of forums, and then iterates through them using the template language. How can it invoke the method on the forum for the latest post that needs the 'user' variable from the template context? The template language lets me say 'forum.latest_post' but I need to pass in 'user'. 'forum.latest_post(user)' does not work because the template language does not allow it. This tag lets me specify an object, the method on that object to call, and the variable to pass to that method. It is not the prettiest thing but with this add on you can do: `{% method_arg forum latest_post user as post %}`

• tags

Sun 11 Jul 2010 Read More

The chunkmaker

This is a general-purpose utility function, but since it uses lazy sequences via itertools, so it should be suitable for use with Querysets.

• python
• utility
• sequence
• itertools

Sun 11 Jul 2010 Read More

really_equals

Lets you compare two objects based on fields

• object
• comparison

Sun 11 Jul 2010 Read More

real_printf

Allows you to use the N argument parameters in a printf string

• printf

Sun 11 Jul 2010 Read More

several_random template filter

Allows the selection of one or more items from a list. The built-int `random` filter only allows you to select a single at a time, and repeated use can return the same item many times. **Example:** `{% for random_item in item_list|several_random:3 %} ... {% endfor%}` **Note:** If you're running this on an uncached QuerySet, it can result in many database queries... a future improvement might check to see if the passed object is a QuerySet and act accordingly.

• filter

Sun 11 Jul 2010 Read More

Sphinx Search ORM

An ORM model for the Sphinx full-text search engine. See http://www.sphinxsearch.com/ for more information. It currently supports the following: class MyModel(models.Model): search = SphinxSearch() MyModel.search.query('query') MyModel.search.query('query').order_by('@weight', '@id', 'my_attribute') MyModel.search.query('query').filter(my_attribute=5) MyModel.search.query('query').filter(my_other_attribute=[5, 3,4]) MyModel.search.query('query').exclude(my_attribute=5)[0:10] MyModel.search.query('query').count() SphinxSearch().query('hello').on_index('model_myapp model_myotherapp') Returns an ordered list of the objects in your database. -- Update: New Methods: * count() * index_on(<str index>) * extra(<see django>) * all() (does nothing) * select_related(<see django>) * group_by(<str attribute>, <const function>[, <str sort>) * weights(<list weights>)

• search
• sphinx
• full-text

Sun 11 Jul 2010 Read More

form_for_model / instance customized save and model aware validation

A way to make form_for_model more customizable.

• form_for_model
• form_for_instance
• model
• form
• baseform

Sun 11 Jul 2010 Read More

SQLite database vacuum script

This script can be run periodically (e.g. as a nightly cronjob) to keep a SQLite database with high churn from growing unnecessarily large.

• db
• utility
• sqlite

Sun 11 Jul 2010 Read More

custom css classes for newforms

This isn't really any trick, its just that I didn't find any documentation of this or any references in searching. There are a few changes proposed for css classes which might make this redundant, but for now this works! If you want to add attributes for any fields, just include them in the widget constructor. They get written out in key value pairs when the input field is being created. e.g. in the example above, this will come out like: ` '<input type="text" name="start_date" id="id_start_date" class="vDateField required" size="10"/>' `

• newforms
• css

Sun 11 Jul 2010 Read More

Adding a field to a newform in __init__

When adding fields in the __init__ of a newform, and you don't want the fields to be added *after* the class-attribute fields, this is a possibility... This is a bad example as the email_from could just as well have been defined as a class variable!

• newforms
• field
• init

Sun 11 Jul 2010 Read More

Strip trailing .html extensions from URLs so that existing bookmarks work for a legacy site ported to Django

1) You've ported an existing web site to Django. 2) The new site URLs don't have html (or htm) extensions. 3) The old site had URLs with html extensions. 4) You want existing bookmarks to work. Use this middleware to removes trailing .htm and .html extensions from incoming URLs (GETs only) so that your new site honors existing bookmarks. Locate it in settings.MIDDLEWARE_CLASSES near CommonMiddleware because it has similar middleware stack location requirements. If an incoming URL has an html extension, ZapDotHtmlMiddleware strips it out and redirects.

• middleware
• url_rewrite
• strip_dot_html_from_urls

Sun 11 Jul 2010 Read More

escape() -- works on dictionaries/lists

Works just like the normal template filter, escape(), except that it works on dictionaries and lsits

• escape

Sun 11 Jul 2010 Read More

custom sql without table names

Keeps database table names out of custom SQL code, but still allows for correct parameter passing in the execute function. (psycopg doesn't substitute table or field names, only data, in the execute function)

• sql
• postgres

Sun 11 Jul 2010 Read More

Getting the global error of a form

You may want to access to "global" errors in your template, typically when you have a custom `clean()` method which checks several fields. `{{ form.errors }}` gives an < ul >, which is often not what you want, and `{{ form.errors|join:", " }}` iterates in the keys of `errors` (which are the names of fields, uninteresting). The global `errors`'s key is "__all__", and Django doesn't allow us to do `{{ form.errors.__all__ }}`. This method returns an array, like a classic `{{ form.field.errors }}`, and can be used with a join : `{{ form.get_global_errors|join:", " }}`.

• newforms
• forms

Sun 11 Jul 2010 Read More

Ordered items in the database

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).

• db
• orm
• database
• plugin
• mixin

Sun 11 Jul 2010 Read More