how to register a tag in HTML django to make a string lowercase?

Question

I have a python list, iterated over to display a bullet point list on a web page. I want to make each entry in the list lower case, but still keep the original case for what get's displayed.

I'm getting the following warning via Django below:

TemplateSyntaxError at /
Invalid block tag on line 12: 'catEntry', expected 'empty' or 'endfor'. Did you forget to register or load this tag?

My html:

{% extends "cats/layout.html" %}

{% block title %}
    cats
{% endblock %}

{% block body %}
    <h1>All cats</h1>

    <ul>
        {% for entry in entries %}
        {% newEntry= entry.lower() %} 
            <li><a href = 'cats/{{newEntry}}.md' </a>{{ entry }}</li>
        {% endfor %}
    </ul>

{% endblock %}

thanks

Answer 1

{% filter force_escape|lower %}
    This text will be HTML-escaped, and will appear in all lowercase.
{% endfilter %}

ref: https://docs.djangoproject.com/en/3.2/ref/templates/builtins/