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How to Create and Use Custom Filters in Django HTML Templates?

To add custom filters in a Django HTML template, you can follow these steps:

  1. Create a Custom Filter Function: You need to create a Python function that defines your custom filter logic. This function should accept one or more arguments and return the filtered output.
  2. Register the Filter Function: You'll need to register your custom filter function with Django's template system. This is typically done in a Django app's templatetags directory.
  3. Use the Custom Filter in Your HTML Template: After registering the custom filter, you can use it in your HTML templates by loading the filter library and applying the filter to a variable or expression.

Here's a step-by-step guide:

Step 1: Create a Custom Filter Function 

Let's say you want to create a custom filter to capitalize the first letter of each word in a string. You can define your custom filter function like this:

   
    # myapp/templatetags/custom_filters.py
    from django import template

    register = template.Library()

    @register.filter
    def capitalize_words(value):
        return ' '.join(word.capitalize() for word in value.split())


Step 2: Register the Filter Function

Make sure that your custom filter function is located in a Python file inside a templatetags directory of one of your Django apps. In this example, it's in a file called custom_filters.py. You'll also need to create an empty __init__.py file in the templatetags directory to make it a Python package.

# myapp/templatetags/custom_filters.py
    TEMPLATE_LOADERS = [
        'django.template.loaders.app_directories.Loader',
        'myapp.templatetags.custom_filters',
    ]
   

Step 3: Use the Custom Filter in Your HTML Template

In your HTML template, load the custom filter library at the top of the file and then apply the filter to a variable or expression using the | symbol:

   
    {% load custom_filters %}

    <!DOCTYPE html>
    <html>
    <head>
        <title>Custom Filter Example</title>
    </head>
    <body>
        <p>{{ some_text|capitalize_words }}</p>
    </body>
    </html>


In this example, some_text is the variable you want to apply the custom filter to, and capitalize_words is the name of the custom filter function you defined earlier.

That's it! When you render this template with your Django view, the capitalize_words filter will be applied to the some_text variable, capitalizing the first letter of each word in the output.

Other custom filter examples:



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