Run Python in Your HTML Via a Custom Django Template Tags Filter
This post shows how to set up a custom Django template tag filter. With help from Django's load built-in, you can execute a Python function from your app's HTML. In this example, the function returns the quotient, or result of dividing two numbers. Mathematics and Python for the win!
I worked some of this out with help from Bing and following along with the Django custom template tags documentation.
Install Django Python Library
pip install Django
Create templatetags.py
I created a "templatetags" folder in the app folder and placed templatetags.py within it. The Django docs recommend your app's folder. Below, the @register.filter decorator registers the divide function so Django knows it exists.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 | from django import template register = template.Library() @register.filter def divide(value, divisor): """A Django filter that accepts 2 arguments: 1. value, number to be divided 2. divisor, number to divide by Returns the quotient in hundredths decimal format. """ # Check if the argument is zero to avoid division by zero error. if divisor == 0: return None quotient = value / divisor return f"{quotient:.2f}" |
Edit Your HTML Code to Call the Divide Function
1 2 3 4 5 6 7 8 9 10 11 12 13 | {% extends 'base.html' %}
{% block content %}
{% load templatetags %}
<div class="container" style="display: inline-block; inline-size: 90%; block-size: auto; writing-mode: horizontal-tb;">
{% for hotel in hotels %}
<div class="row row-cols-3" style="display: flex; justify-content: flex-end; padding: 10px; margin: 10px; background-color: #f0ffff; box-shadow: 5px 5px 10px gray; border-radius: 10px;">
<div class="col">
<h5 style="color: green;">Peso: ${{ hotel.price }}</h5>
<h5 style="color: gray;">USD: ${{ hotel.price|divide:18.9 }}</h5>
</div></div>
{% endfor %}
</div>
{% endblock %}
|
In the HTML, call the divide function by loading the templatetags module and then passing two numeric arguments:
{{ hotel.price|divide:18.9 }}
- A number to be divided, here the hotel price from a "Hotel" DB model
- The function name to call and a number to divide by. Here we use "divide:18.9" to approximately convert Mexican pesos to US dollars. Recently, the exchange rate fluctuates in the 17-19 pesos per dollar range.
Basic Hotel Model Example
1 2 3 4 5 6 7 8 9 | from django.db import models class Hotel(models.Model): name = models.CharField(max_length=200) price = models.DecimalField(max_digits=10, decimal_places=2) address = models.CharField(max_length=200) city = models.CharField(max_length=200) all_inclusive = models.BooleanField() photo = models.ImageField(upload_to="media") |
Register Model in admin.py
1 2 3 4 | from django.contrib import admin from .models import Hotel admin.site.register(Hotel) |
I was pleased to be able to make some on the fly mathematic calculations in my HTML with a custom Django filter!
