Creating a custom template tag in Django.

my_template.html

{% load my_template_tag %}  <!-- Loading the file we defined our template tags in -->

{% for pdt in products %}
<tr>
  <td>{{pdt.name}}</td>
  <td>{{pdt.price}}</td>
  <td>{{pdt.sold_by}}</td>
  <td>{% n_reviews pdt.id %}</td> 
            <!-- our template tag, pdt.id is passed as argument in n_reviews function -->
 </tr>
{% endfor %}

my_template_tag.py

from django import template
from some_app.models import Product, Review             # say, we have, Product, Review in our some_app/models.py

register = template.Library()

@register.simple_tag
def n_reviews(product_id):
  
  # write down your queries.
  # example queries..
  # here, let's say we wanna count the number of reviews on a certain product. We can do something like this.
  
  product = Product.objects.get(id=product_id)
  reviews = Review.objects.filter(reviewed_on=product)
  return reviews.count()

outline.txt

<--------------We use custom template tags for the part of information that we need to access a lot of times--------------->
<--------------Ex: To show the number of products in a cart, which is present on the navbar of all pages------------------->

1) Before making a custom template tag, make sure you've added your app name to INSTALLED_APPS (in settings.py).
2) Let app name be my_app , create a directory named 'templatetags' in my_app.
3) Inside 'templatetags', create '__init__.py' and 'my_template_tag.py'