Introduction to Context Processors

What a Context Processor Does

Instead of manually adding a variable to every view's context dict, a context processor injects it into every template's context automatically.

Example: What a Context Processor Does

This plain Python function returns a dict; once registered, every template gains access to {{ site_name }} without any view passing it explicitly.

def site_settings(request):
    return {'site_name': 'CookiesCursor'}

Registering a Context Processor

Custom context processors must be listed by their dotted path in settings.py's TEMPLATES configuration.

Warning: The function must be listed by its full import path (e.g. 'myapp.context_processors.site_settings').

Example: Registering a Context Processor

After registering it, {{ site_name }} becomes usable in any template rendered with render(), with no per-view work.

TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        'OPTIONS': {
            'context_processors': [
                'django.template.context_processors.request',
                'django.contrib.auth.context_processors.auth',
                'myapp.context_processors.site_settings',
            ],
        },
    },
]

Using the Built-in auth Context Processor

django.contrib.auth.context_processors.auth is enabled by default in new projects and makes {{ user }} available in every template.

Example: Using the Built-in auth Context Processor

{{ user }} is available here purely because of the built-in auth context processor -- no view code passed it in.

{% if user.is_authenticated %}
  <p>Welcome, {{ user.username }}!</p>
{% else %}
  <p>Please log in.</p>
{% endif %}