Django http404 error urlconf confusion - django

Question

I was really confused why I was receiving Http404 error. To be more clear heres my code:
My app named books
views.py
from django.shortcuts import render_to_response
from django.http import Http404
from django.template import RequestContext
from books.models import *
def index(request):
title = 'Book Gallery'
books = Book.objects.all().order_by('-id')
lang_list = Lang.objects.all().order_by('-lang')
template = 'books/index.djhtml'
context = {'books': books, 'title': title, 'lang_list': lang_list}
return render_to_response( template, context, context_instance=RequestContext(request) )
def by_book_slug(request, bookslug):
slug = bookslug
try:
book = Book.objects.get(slug=slug)
except:
raise Http404
title = book.name
template = 'books/singlebook.djhtml'
context = {'book': book, 'title': title}
return render_to_response( template, context, context_instance=RequestContext(request) )
def by_lang_slug(request, langslug):
filter = langslug
try:
language = Lang.objects.get(slug=filter)
except:
raise Http404
lang_list = Lang.objects.all().order_by('-lang')
books = Book.objects.filter(lang=language).order_by('-id')
title = language
template = 'books/by_language.djhtml'
context = {'books': books, 'title': title, 'filter': filter, 'lang_list': lang_list}
return render_to_response( template, context, context_instance=RequestContext(request) )
urls.py inside my book app folder
from django.conf.urls import patterns, include, url
from books import views
urlpatterns = patterns('',
url(r'(?P<langslug>.*)/$', views.by_lang_slug, name='by_lang'),
url(r'(?P<bookslug>.*)/$', views.by_book_slug, name='by_book'),
url(r'^$', views.index, name='book_gallery'),
)
link that pertains to langslug url conf works but those links for bookslug url conf does not work. When I try to switch them down and up, one of them work and the other one is not.
I really don't know what is happening here. Any help will be a great help. Thanks.
the index template of my books app
{% extends 'base.djhtml' %}
{% block title %} | Gallery{% endblock %}
{% block stylesheets %}
<link rel="stylesheet" type="text/css" href="{{ STATIC_URL }}css/style.css" />
{% endblock %}
{% block content_header %}
{% endblock %}
{% block content_body %}
<div class="row">
<div class="span3">
<strong>filtered by >
{% if filter %}
{{ filter }}
{% else %}
All
{% endif %}
</strong>
<ul class="nav nav-list">
<li class="nav-header">Filter</li>
<li class="nav-header
{% if not filter %}
active
{% endif %}
">All</li>
{% for list in lang_list %}
<li class="nav-header
{% if filter == list.slug %}
active
{% endif %}
">
{{ list.lang }}
</li>
{% endfor %}
</ul>
</div>
<div class="span9">
{% for book in books %}
<div class="span3">
<a href="{{ book.book_cover.url }}">
<img alt="{{book.name}}" src="{{ book.thumbnail.url }}" />
</a>
<h4>{{book.name}}</h4>
<p>{{book.desc|truncatewords:15}}</p>
View more...
</div>
{% endfor %}
</div>
</div>
{% endblock %}
The by_language template for my book app
{% extends 'base.djhtml' %}
{% block title %} | Gallery{% endblock %}
{% block stylesheets %}
<link rel="stylesheet" type="text/css" href="{{ STATIC_URL }}css/style.css" />
{% endblock %}
{% block content_header %}
{% endblock %}
{% block content_body %}
<div class="row">
<div class="span3">
<strong>filtered by >
{% if filter %}
{{ filter }}
{% else %}
All
{% endif %}
</strong>
<ul class="nav nav-list">
<li class="nav-header">Filter</li>
<li class="nav-header
{% if not filter %}
active
{% endif %}
">All</li>
{% for list in lang_list %}
<li class="nav-header
{% if filter == list.slug %}
active
{% endif %}
">
{{ list.lang }}
</li>
{% endfor %}
</ul>
</div>
<div class="span9">
{% for book in books %}
<div class="span3">
<a href="{{ book.book_cover.url }}">
<img alt="{{book.name}}" src="{{ book.thumbnail.url }}" />
</a>
<h4>{{book.name}}</h4>
<p>{{book.desc|truncatewords:15}}</p>
View more...
</div>
{% endfor %}
</div>
</div>
{% endblock %}
I have included a raise Http404 method when specified slug does not match to any query in the database. The thing I was confused about is, when I try to switch langslug and bookslug urlconf, links that are associated to one of these url works and the other is not.

Answer 1

Based on your url, if I put value on it even though they have different view, the result would be:
urlpatterns = patterns('',
# http://localhost:8000/English/
url(r'(?P<langslug>.*)/$', views.by_lang_slug, name='by_lang'),
# http://localhost:8000/YourBook/
url(r'(?P<bookslug>.*)/$', views.by_book_slug, name='by_book'),
# http://localhost:8000/
url(r'^$', views.index, name='book_gallery'),
)
Have you notice it, they have the same pattern so the first view execute is the by_lang_slug. So if you change the order the other one will be executed first. The best thing to do about it is to have a unique url name.
urlpatterns = patterns('',
# http://localhost:8000/lang/English/
url(r'lang/(?P<langslug>.*)/$', views.by_lang_slug, name='by_lang'),
# http://localhost:8000/book/YourBook/
url(r'book/(?P<bookslug>.*)/$', views.by_book_slug, name='by_book'),
# http://localhost:8000/
url(r'^$', views.index, name='book_gallery'),
)
Now they are different....