Override existing Django Template Tags

Question

Is it possible to override an existing Django Template Tag or is it necessary to customize the template file and create a new Template Tag?

Answer 1

Yes.

As django is basically a python library (as with everything in python) you can over-write anything you'd like.

It's not clear exactly what you'd like to do but it really is pretty easy to roll-your-own templatetag, the docs are pretty clear: https://docs.djangoproject.com/en/dev/howto/custom-template-tags/#writing-custom-template-tags

This is crazy basic but this is the kind of template I use to start building a custom template tag from:

myapp/templatetags/my_custom_tags.py (must have __init__.py in this directory)

from django import template
register = template.Library()

class CustomTag(template.Node):
    def render(self, context):
        context['my_custom_tag_context'] = "this is my custom tag, yeah"
        return ''

@register.tag(name='get_custom_tag')
def get_custom_tag(parser, token):
    return CustomTag()

Usage in your template goes like this:

{% load my_custom_tags %}
{% get_custom_tag %}
{{my_custom_tag_context}}

You probably want to parse the token, and you probably want some kind of __init__ in the class, but it does go to show how basic it is.

---

You can browse through the existing 'default' templatetags, replicate and modify them to your heart's content.

There really is some great stuff there: https://github.com/django/django/blob/master/django/template/defaulttags.py

Answer 2

I was looking for the same answer, so figured I'd share my solution here. I wanted to override the default url template tag in django without having to use a custom template tag and load it in every template file.

The goal was to replace %20 (spaces) with + (pluses). Here's what I came up with...

In __init__.py

from django.template.defaulttags import URLNode

old_render = URLNode.render
def new_render(cls, context):
  """ Override existing url method to use pluses instead of spaces
  """
  return old_render(cls, context).replace("%20", "+")
URLNode.render = new_render

This page was useful https://github.com/django/django/blob/master/django/template/defaulttags.py

Answer 3

I assume by "an Existing Django Template Tag" you mean a tag in a different app.

Create a templatetags/tagfile.py that registers a tag with the same name. Make sure that tagfile is the same name that the template loads with {% load tagfile %} for getting the original tag.

Also, make sure your app is listed after the original app in INSTALLED_APPS.

Answer 4

I am pretty sure you are asking for complete override of a django templatetag.

The short answer is - Yes, you can override an existing templatetag.

Here is how to achieve it:

• You have to have your template directory included in the settings:

    TEMPLATES = [
        {
            'BACKEND': 'django.template.backends.django.DjangoTemplates',
            'DIRS': [os.path.join(BASE_DIR, 'your_app/templates')],
            'APP_DIRS': True,
            'OPTIONS': {
                'context_processors': [
                    'django.template.context_processors.debug',
                    'django.template.context_processors.request',
                    'django.contrib.auth.context_processors.auth',
                    'django.contrib.messages.context_processors.messages',
                    'django.template.context_processors.static',
                ],
            },
        },
    ]

• You have to include the app you want to override a templatetag for, in the INSTALLED_APPS:

INSTALLED_APPS = [
        'django.contrib.admin',
        'django.contrib.auth',
        'django.contrib.contenttypes',
        'django.contrib.sessions',
        'django.contrib.messages',
        'django.contrib.staticfiles',
        'your_app_name',
        ...
    ]

The important bit is to have your app after django's apps !

This is due to the way django works. We will get use right of that.

• Now, create a folder inside your app, named templatetags. It is important to have __init__.py file inside the templatetags, so django could understand it is a python package!:

your_app_name/templatetags/__init__.py.

• Create the templatetag you want to override. In that example, i'll use the admin_list.py tag.

In that case, it should be placed like this:

your_app_name/templatetags/admin_list.py

• Now copy the entire content of the admin_list.py (VERY IMPORTANT!) from django.contrib.admin.templatetags.admin_list.py and modify whatever you want.

It is important to have the whole content of the django's admin admin_list.py and not only a piece of code, else it would not work!

---

How it works: Django is looking in your application for templatetags folder and uses the template tags inside of it. It places yours template tags after the admin's ones and in short - it overrides them since they are placed after django.admin in the INSTALLED_APPS.

Do not forget to:

• ./manage.py collectstatic
• set DEBUG = False

in production.

I have tested it already for result_list(cl) function override, and it is working.

---

This solution works event without custom html template files.

Hope that helps.

Answer 5

If you don't want to depend on the order of your app inside the settings.py INSTALLED_APPS, then you can try the following:

Create the templatetag function/class as usual. Say you want to override a templatetag named otherapp_tags.current_time from an app named other_app. First, create your own version of that function/class:

def my_current_time(format_string):
    return datetime.datetime.now().strftime(format_string)

then, instead of registering this function/class inside YOUR apps namespace, patch the existing function from the other app:

from other_app.templatetags import otherapp_tags

otherapp_tags.register.tags['current_time'] = my_current_time

Typically you should do this inside your AppConfig's ready() method.

Answer 6

The actually most voted solution has one major drawback for me - you need to redefine all tags. For some projects, that can be a big drawback. How to solve that? As mentioned by m_floer, it's best to import the register instance from the outside module. So how it should look? Code was taken from Django Jazzmin:

What I want to do? Overwrite the only one template tag: get_side_menu tag.
The tag is located in jazzmin.templatetags.jazzmin, so in our app we will create module templatetags with file jazzmin.py. And the contents will be:

...
from jazzmin.templatetags.jazzmin import register


@register.simple_tag(takes_context=True, name="get_side_menu")
def get_side_menu(context: Context, using: str = "available_apps") -> List[Dict]:
    ...  # your template tag code

This will override just and only selected Django template tag in the easiest way possible. Be aware, that it's for all apps in the given project!