Working with filters in Jinja2

# Working with filters in Jinja2

# In this video... (TL;DR)

TIP

List of all code changes made in this lecture: https://diff-store.com/diff/section09__03_jinja2_filters (opens new window)

In a nutshell, filters are to Jinja what functions are to Python. They take inputs, and return outputs. We use them where we use values, to transform them.

{% set num_todos = todos | length %}

There are a lot of built-in filters!

capitalize()
default()
escape()
first()
format()
groupby()
join()
last()
length()
reverse()
Lots more!
Plus we can create our own (more on that later)

# Code at the start of this lecture

{% set num_todos = len(todos) %}
{% if num_todos > 0 %}
    <p>You have {{ num_todos }} things to do today.</p>
{% else %}
    <p>Nothing to do today. Relax!</p>
{% endif %}

# Code written in this lecture

{% set num_todos = todos | length %}
{% if num_todos > 0 %}
    <p>You have {{ num_todos }} things to do today.</p>
{% else %}
    <p>Nothing to do today. Relax!</p>
{% endif %}

We've already seen code that uses filters before:

<article class="entry">
  <div>
    <h2 class="entry__title">{{ entry[0] | truncate(30, true) }}</h2>
    <time class="entry__date" datetime="{{ entry[1] }}">• {{ entry[2] }}</time>
  </div>
  <p class="entry__content">
    {{ entry[0] }}
  </p>
</article>

# Final code at the end of this lecture

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Todos</title>
</head>
<body>
  {% set num_todos = todos | length %}
  {% if num_todos > 0 %}
      <p>You have {{ num_todos }} things to do today.</p>
  {% else %}
      <p>Nothing to do today. Relax!</p>
  {% endif %}
</body>
</html>

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