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