Motivation and tactics to switch a production site from Django templates to Jinja2 templates

1. A Two-step Dance with
Django and Jinja2
Templates
Sebastien Mirolo
@seabasscapoeira
smirolo@djaodjin.com

2. Motivation

3. Where we started
- 80 template files
- 4.3K lines of HTML template code
+ Customers relying
on site to process payments

4. The Plan
Deploy Django /
Jinja2 compatible
subset
Feature flag to
toggle between
template pipelines

5. An Easy Bit
{% csrf_token %}
-{% csrf_token %}
+<input type="hidden" name=“csrfmiddlewaretoken"
value="{{csrf_token}}">

6. The Good Old Times
$ cat base.html
{% block bodyscripts %}
<script type="text/javascript" charset="utf-8"
src=“/assets/base.js"></script>
{% block base_bodyscripts %}{% endblock %}
{% endblock %}
$ cat index.html
{% extends "base.html" %}
{% block bodyscripts %}
{% block base_bodyscripts %}
{{ block.super }}
<script type="text/javascript" charset="utf-8"
src="/assets/index.js"></script>

7. Undefined Context
Variables
{% if urls.profile %}
<a href="{{urls.profile}}">My Profile</a>
{% endif %}

8. When everything can
be solved with a filter
$ cat
templatetags/authenticated_tags.py
...
@register.filter()
def is_authenticated(request):
return hasattr(request, 'user') and
request.user.is_authenticated()
$ cat index.html
{% if request.user|is_authenticated %}
...
{% endif %}
is_authenticated
vs.
is_authenticated(
)
capfirst
vs.
capitalize

9. Moving Python code
into Templates
• crispy
• {% include with %} vs. {% macro
%}

10. Moving Template
code into Python
• URL patterns
• {% if forloop.counter0|divisible_by:3 %} vs. {% if
loop.index is divisibleby 3 %}

11. Jinja2 rendering
pipeline quirks
• Template loaders
• Cache dimensioning
• Optimizer in a multi-tier context

12. How you can help?
• Clone DjaoDjin repos and try them
out!
• Star us on GitHub!
https://github.com/djaodjin/djaodjin-pages/
https://github.com/djaodjin/djaodjin-saas/

13. Thank You
Sebastien Mirolo
@seabasscapoeira
smirolo@djaodjin.com