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Python Customizing Django Templates Building Custom Tags Complex Template Tags

Posted by Will Anderson
Will Anderson
28,683 Points

Server error 'not a registered tag library' when rendering site for Complex Template Tags. Redone to teacher's code 4X.

Here's the website description:

Request Method: GET
Request URL:    http://port-8000-c9y6cyrl64.treehouse-app.com/
Django Version: 1.9.9
Exception Type: TemplateSyntaxError
Exception Value:    
'course_extras' is not a registered tag library. Must be one of:
admin_list
admin_modify
admin_static
admin_urls
cache
future
humanize
i18n
l10n
log
static
staticfiles
tz
Exception Location: /usr/local/pyenv/versions/3.5.0/lib/python3.5/site-packages/django/template/defaulttags.py in find_library, line 1136
Python Executable:  /usr/local/pyenv/versions/3.5.0/bin/python
Python Version: 3.5.0
Python Path:    
['/home/treehouse/workspace/learning_site',
 '/usr/local/pyenv/versions/3.5.0/lib/python35.zip',
 '/usr/local/pyenv/versions/3.5.0/lib/python3.5',
 '/usr/local/pyenv/versions/3.5.0/lib/python3.5/plat-linux',
 '/usr/local/pyenv/versions/3.5.0/lib/python3.5/lib-dynload',
 '/usr/local/pyenv/versions/3.5.0/lib/python3.5/site-packages']
Server time:    Fri, 21 Jul 2017 13:53:32 -0700

Here's course_extras.py

from django import template

from courses.models import Course


register = template.Library()

@register.simple_tag
def newest_course():
    ''' Gets the most recent course added to the Library. '''
    return Course.objects.latest('created_at')

@register.inclusion_tag('courses/course_nav.html')
def nav_courses_list():
    ''' Returns dictionary of courses to display as navigation pane '''
    courses = Course.objects.all()
    return {'courses': courses}

<head-desk>

[MOD: added ```python formatting -cf]

Chris Freeman: <head-desk> is not part of the code. That is a cryptic piece of an illustration of me pounding my head into my desk over this situation. I'm sorry it got added to the code I was working with, it does not belong there.

Will Anderson
Will Anderson
28,683 Points

Here's the source of the exception, layout.html:

{% load static from staticfiles %}
{% load course_extras %}

<!doctype html>
<html>
    <head>
        <title>{% block title %}{% endblock %}</title>
        <link rel="stylesheet" href="{% static 'css/layout.css' %}">
        {% block static %}{% endblock %}
    </head>
    <body>
        <div class="site-container">
            <div>{% nav_courses_list %}</div>
            <nav>
                <a href="{% url 'views.hello_world' %}">Home</a>
                <a href="{% url 'courses:list' %}">Courses</a>
            </nav>
            <p>Don't miss our latest course, {% newest_course %}!</p>
            {% block content %}{% endblock %}
        </div>
    </body>
</html>

[MOD: added ```html+jinja formatting -cf]

Chris Freeman
Chris Freeman
Treehouse Moderator 68,441 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,441 Points

What is the <head-desk> in the course_extras.py file? It could be stopping the compilation of the file course_extras.py which would case the library not to be found.

1 Answer

Will Anderson
Will Anderson
28,683 Points

Solved. Added '{% load course_extras %}' both course_detail.html and step_detail.html. This wasn't covered in the video so it's surprising that the instructor's example passed the rules engine when without it, the current engine fails the code.