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fatbox-django-utils 1.1

A collection of Django utilities, built by FatBox

Latest Version: 1.2

This is a collection of general utilities for Django projects built by FatBox.

Installation

Install using pip:

pip install fatbox-django-utils

If you're going to use the Template Tags then you also need to add fatbox_utils to your INSTALLED_APPS setting.

These utilities require Django 1.3+. They may work with earlier versions but haven't been tested.

Rendering templates

render_to decorator

The render_to decorator allows you to very easily render templates from your view functions. Simply decorate your view function and specify the name of the template to render to, then return a dict from your view function that contains variables that will be in the context when rendering the template.

from fatbox_utils.decorators import render_to

@render_to('myapp/template.html')
def myview(request):
    return {
        'var1': var1,
        'var2': var2
    }

You can change the template on the fly by returning a list or tuple where the first element is the name of the template and the second element is the dict to use for the context.

@render_to('myapp/template.html')
def myview(request):
    context = {
        'var1': var1,
        'var2': var2
    }

    # if something is true then use our other template
    if something_is_true:
        return ('other_template.html', context)

    # otherwise use the default template
    return context

Lastly if you don't return a dict or a list/tuple then render_to will just return what you give it. This ensures that if you return things like HttpResponseRedirect objects they will work as expected, but also means that you are free to craft your own response should it be required. Anything that's valid to return from a standard Django view will work.

Humanize

humanize_time function

The humanize_time function summarizes time based on the units you provide to it. For example here is what is run in the doc tests:

>>> from fatbox_utils.humanize import humanize_time
>>> humanize_time(173, "hours")
u'1 week, 5 hours'
>>> humanize_time(17313, "seconds")
u'4 hours, 48 minutes, 33 seconds'
>>> humanize_time(5400, "seconds")
u'1 hour, 30 minutes'
>>> humanize_time(90, "weeks")
u'1 year, 10 months, 2 weeks'
>>> humanize_time(42, "months")
u'3 years, 6 months'
>>> humanize_time(500, "days")
u'1 year, 5 months, 3 weeks, 3 days'

See: http://stackoverflow.com/a/6574789

Cache

delete_template_fragment_cache function

This is a function that deletes a named template fragment cache.

See: http://djangosnippets.org/snippets/2723/

In your template:

{% load cache %}

{% cache 3600 my_cache_block request.user.username %}
...
{% endcache %}

And in your view:

from fatbox_utils.cache import delete_template_fragment_cache

def my_view(request):
    ...
    delete_template_fragment_cache("my_cache_block", request.user.username)
    ...

i18n / Translation

This package includes a number of different utilities for managing and working with i18n / translation in your project.

current_lang context processor

This is a context processor that adds current_lang to your template context as a 2 letter language code (ie. en, fr, pt, etc).

Just add fatbox_utils.context_processors.current_lang to the TEMPLATE_CONTEXT_PROCESSORS setting.

ManualLanguageMiddleware

This is a middleware class that allows you to force the language used by the Django translation layer based on a querystring parameter.

To use it simply add fatbox_utils.middleware.ManualLanguageMiddleware to the MIDDLEWARE_CLASSES setting. Then you can pass a two character language code to a get parameter named lang to activate a specific language.

translatable_property for Models

Often times when working on a project that deals with multiple languages you want to have certain properties of a model translatable. The translatable_property class provides a convenient interface to define your properties that should be available in multiple languages.

Consider the following example models.py file:

from django.db import models
from fatbox_utils.i18n import translatable_property

class Event(models.Model):
    start = models.DateTimeField()
    end = models.DateTimeField()

    title = translatable_property('title', 'descriptions')
    details = translatable_property('details', 'descriptions')

class EventDescription(models.Model):
    event = models.ForeignKey(
        Event,
        related_name='descriptions'
    )
    language = models.CharField(
        max_length=2,
        help_text="The ISO two character language code (en, fr, es, pt, etc)"
    )
    title = models.CharField(
        max_length=32
    )
    details = models.TextField()

What this does is add two models Event and EventDescription where the EventDescription model has a foreign key to Event and sets up a related manager named descriptions.

On the Event model we define two properties using the translatable_property class. When defining these properties the first argument is the field on the related model and the second argument is the name of the manager that we can use to lookup the related model that corresponds to the current language.

When you access one of the translatable_property properties on your model it will try to fetch the related object from the descriptions manager where the related object has a field named language that matches the current language, as defined by the get_language function from the django.utils.translation package. If it can't find a related object with a matching language field it will then try to get one with the default language, as defined by settings.DEFAULT_LANGUAGE.

Performance Optimization

If you don't do any optimization of your querysets once you reach even a modest number of Event objects iterating over their querysets can become a HUGE burden on your database due to the number of SELECT lookups it needs to do when fetching all of the related EventDescription objects.

To combat this you can use Django's prefetch_related queryset function to fetch all of the related descriptions in one fell swoop, reducing the number of queries to 2.

Event.objects.filter(...).prefetch_related('descriptions')

Admin Integration

Once you have your models setup with translatable_property then you can simply use normal Django Inlines without having to worry about complex admin site configuration.

Template Tags

Smart Spaceless

The Django {% spaceless %} tag is a great way to optimize your templates so that you send the smallest amount of data possible to clients, however when you're in development turning spaceless on makes it hard to read your HTML and debug problems.

The {% smart_spaceless %} tag works exactly the same as the normal tag, except that it only applies spaceless when your DEBUG setting is False.

{% load smart_spaceless %}{% smart_spaceless %}
<!doctype html>
<html>
...
</html>
{% end_smart_spaceless %}

URL Tools

The URL Tools template tags provide some convenience functions when working with URLs in your templates. They all require that the request be available in the current context so make sure that you have django.core.context_processors.request enabled in your TEMPLATE_CONTEXT_PROCESSORS setting.

build_absolute_uri

This exposes the build_absolute_uri function of the request object to your templates.

{% load urltools %}

<a href="{% build_absolute_uri myobject.get_absolute_url %}">Link</a>

modify_querystring

This allows you to modify individual querystring parameters, without needing to reconstruct the entire URL.

For example, say you're on a page that shows a listing of objects and you have flags for determining if the user will view the results as a grid or as a list. On this same view you may accept a querystring parameter to further limit the query so having to manually reconstruct the URL just to change the format becomes a much more complex task. With modify_querystring we can change just the format querystring parameter (even adding it if it doesn't exist) without having to reconstruct anything.

{% load urltools %}

<div>
  <span>Sort:</span>
  <a href="{% modify_querystring sort="date" %}"{% if sort_by == "date" %} class="active"{% endif %}>By Date</a> |
  <a href="{% modify_querystring sort="title" %}"{% if sort_by == "title" %} class="active"{% endif %}>Alphabetically</a>
</div>

<div>
    <span>View as:</span>
    <a href="{% modify_querystring format="list" %}" {% if page_format == "list"%}class="active"{% endif %}>List</a> |
    <a href="{% modify_querystring format="grid" %}" {% if page_format == "grid"%}class="active"{% endif %}>Grid</a>
</div>
 
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