This Week in Django is a weekly podcast about all things Django.
This week we have our special guest Matthew Wensing on the show to discuss his work with the Django GIS Branch (GeoDjango). We also cover EveryBlock, Some cool projects from the community, the Tip of the Week, and a couple of questions from the IRC.
Please see the Show Notes below for all the pertinent information and links
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Show Notes
Big News (1:03)
- EveryBlock The brain child of Adrian Holovaty, EveryBlock is a website that filters an assortment of local news by location so you can keep track of what’s happening on your block, in your neighborhood and all over your city. The first release of EveryBlock contains information for Chicago, San Francisco, and New York. All written in Django.
Branching & Merging (4:10)
Matthew Wensing, co-founder of Stormpulse, joined us to talk about the GIS Branch, also known as GeoDjango.
- PostGIS and the PostGIS IRC Channel
Community Catchup (27:51)
- Django People – Very cool site using google mashups to allow the Django community to get connected.
- Using Git with Django Screencast – As promised, Brian Rosner put together an excellent screencast that gives a nice overview of using Git with Django.
- Per-Function Cache Decorator – Cool snippet that adds a decorator that caches the decorated function for the amount of time specified. Great for expensive operations.
- django-threadedcomments Eric Florenzano announced it on his blog that he worked together with Tony Hauber to create a threaded comments application. Provides threaded comments, a la reddit.com, and completely replaces the current comment system. They even provided a comment migration script.
Tip of the Week (43:40)
The templatetag {% block %} has a not so known variable {{ block.super }}. It is documented, but it seems to be over looked. What this allows you to do is get the rendered output of the parent block and display it as you like. Take the following use case:
In a base.html you have the following bit of code:
{% block title %}My Cool Website{% endblock %}
Then in a template that extends the base.html template you want to be able to display “My Cool Website” as apart of each page:
{% extends "base.html" %}
{% block title %}My Sweet Page | {{ block.super }}{% endblock %}
The will display “My Sweet Page | My Cool Website”.
IRC Ad Nauseam (46:53)
Django IRC FAQ Backwards Incompatible Changes Information
I just upgraded to the latest version and now I’m experiencing Unicode problems:
- Read the Unicode Branch Checklist
- Change the
__str__methods on your models to be__unicode__methods. - Change string literals to be unicode strings. For example:
def __str__(self):
return u'Category: %s' % (self.name,)
I keep getting this error “Reverse query name for field ’%s’ clashes with field ’%s.%s’. Add a related_name argument to the definition for ’%s’.” How do I correct it?
The error message is extremely helpful and tells you what you need to do. There are a lot of different ways this error will appear but usually the fix is the same. You need to specify a related_name argument when defining your field.
The problem often arises because you have two fields on a model that are a ForeignKey to the same table. For instance:
class Episode(models.Model):
pub_date = models.DateTimeField()
title = models.CharField(max_length=255)
slug = models.SlugField(prepopulate_from=("title",), unique=True)
categories = models.ManyToManyField(Category)
body = models.TextField(blank=True)
producer = models.ForeignKey(User, related_name='episode_producers')
host = models.ForeignKey(User, related_name='episode_hosts')
u = User.objects.get(pk=1)
u.episode_producers
u.episode_hosts
Another block trick is to do the following to your
navigation elements:
CSS will take care of highlighting it for you. Nice! Maybe not so Django related but a nice use of the Jinja template paradigm.
Another block trick is to do the following to your <ul> navigation elements:
<ul id=\"{% block page }{ endblock %}\"> <li class=\"front\">Front</li> <li class=\"about\">About</li> </ul>
then in your css do:
ul#front .front, ul#about .about { color: red; }
Now in your templates you can extend the nav block with the name of the page. CSS will take care of highlighting it for you. Nice! Maybe not so Django related but a nice use of the Jinja template paradigm.
The str method should not return Unicode. Replace str with unicode, and in the base Model class there is a default str the encodes the Unicode output.
Very interesting with geodjango. It should be pretty clear to everyone that putting stuff on a map is a huge part of the new wave web, would be really awesome if the gis branch would become a offical part of django.