Context Processors

Remarks#

Use context processors to add variables that are accessible anywhere in your templates.

Specify a function, or functions that return dicts of the variables you want, then add those functions to TEMPLATE_CONTEXT_PROCESSORS.

Use a context processor to access settings.DEBUG in templates

in myapp/context_processors.py:

from django.conf import settings

def debug(request):
  return {'DEBUG': settings.DEBUG}

in settings.py:

TEMPLATES = [
    {
        ...
        'OPTIONS': {
            'context_processors': [
                ...
                'myapp.context_processors.debug',
            ],
        },
    },
]

or, for versions < 1.9:

TEMPLATE_CONTEXT_PROCESSORS = (
    ...
    'myapp.context_processors.debug',
)

Then in my templates, simply:

 {% if DEBUG %} .header { background:#f00; } {% endif %}
 {{ DEBUG }}

Using a context processor to access your most recent blog entries in all templates

Assuming you have a model called Post defined in your models.py file that contains blog posts, and has a date_published field.

Step 1: Write the context processor

Create (or add to) a file in your app directory called context_processors.py:

from myapp.models import Post

def recent_blog_posts(request):
    return {'recent_posts':Post.objects.order_by('-date_published')[0:3],}  # Can change numbers for more/fewer posts

Step 2: Add the context processor to your settings file

Make sure that you add your new context processor to your settings.py file in the TEMPLATES variable:

TEMPLATES = [
    {
        ...
        'OPTIONS': {
            'context_processors': [
                ...
                'myapp.context_processors.recent_blog_posts',
            ],
        },
    },
]

(In Django versions before 1.9, this was set directly in settings.py using a TEMPLATE_CONTEXT_PROCESSORS variable.)

Step 3: Use the context processor in your templates

No need to pass recent blog entries through individual views anymore! Just use recent_blog_posts in any template.

E.g., in home.html you could create a sidebar with links to recent posts:

<div class="blog_post_sidebar">
    {% for post in recent_blog_posts %}
        <div class="post">
            <a href="{{post.get_absolute_url}}">{{post.title}}</a>
        </div>
    {% endfor %}
</div>

Or in blog.html you could create a more detailed display of each post:

<div class="content">
    {% for post in recent_blog_posts %}
        <div class="post_detail">
            <h2>{{post.title}}</h2>
            <p>Published on {{post.date_published}}</p>
            <p class="author">Written by: {{post.author}}</p>
            <p><a href="{{post.get_absolute_url}}">Permalink</a></p>
            <p class="post_body">{{post.body}}</p>
        </div>
    {% endfor %}
</div>

Extending your templates

Context processor to determine the template based on group membership(or any query/logic). This allows our public/regular users to get one template and our special group to get a different one.

myapp/context_processors.py

def template_selection(request):
    site_template = 'template_public.html'
    if request.user.is_authenticated():
        if request.user.groups.filter(name="some_group_name").exists():
            site_template = 'template_new.html'

    return {
        'site_template': site_template,
    }

Add the context processor to your settings.

In your templates, use the variable defined in the context processor.

{% extends site_template %}