Jinja (template engine)

From Wikipedia, the free encyclopedia
Original author(s)Armin Ronacher
Initial releaseJuly 17, 2008; 15 years ago (2008-07-17)[1]
Stable release
3.1.3[2] Edit this on Wikidata / 10 January 2024; 4 months ago (10 January 2024)
Written inPython
TypeTemplate engine
LicenseBSD License
Websitepalletsprojects.com/p/jinja/ Edit this on Wikidata

Jinja is a web template engine for the Python programming language. It was created by Armin Ronacher and is licensed under a BSD License. Jinja is similar to the Django template engine but provides Python-like expressions while ensuring that the templates are evaluated in a sandbox. It is a text-based template language and thus can be used to generate any markup as well as source code.

The Jinja template engine allows customization of tags,[3] filters (for formatting or transforming values[4]), tests (for evaluating conditions[4]), and globals.[5] Also, unlike the Django template engine, Jinja allows the template designer to call functions with arguments on objects. Jinja is Flask's default template engine [6] and it is also used by Ansible,[7] Trac, and Salt.[8] It is also used to make SQL macros, for example for use with dbt.[9]


Some of the features of Jinja are:[10]

  • sandboxed execution
  • automatic HTML escaping to prevent cross-site scripting (XSS) attacks
  • template inheritance
  • compiles down to the optimal Python code just-in-time
  • optional ahead-of-time template compilation
  • easy to debug (for example, line numbers of exceptions directly point to the correct line in the template)
  • configurable syntax

Jinja, like Smarty, also ships with an easy-to-use filter system similar to the Unix pipeline.


The syntax for printing output in Jinja is using the double curly braces, for example {{ Hello, World! }}.

Statements which set variables in jinja or those which do not have an output can be wrapped within {% and %}, using the set keyword. For example {% set foo = 42 %} sets a variable called foo with a value of 42.

Similar to above, comments in jinja can be written using a number sign (#) instead of a percentage (%), for example, {# helpful comment #}.

The syntax for creating a filter in Jinja is a vertical bar (|), for example {{ variable|filter }}. A variable can have multiple filters, for example {{ variable|filter|filter }}).[4]

The syntax for creating a test in Jinja is the keyword is as well as the conditions for evaluating the validity of a test, such as for example {% if variable is divisibleby 10 %}do something{% endif %}).[4]

For loops can be used to iterate over sequences, while retaining their object properties. The following example demonstrates iterating over a list of users with username and password fields.

{% for user in users %}
    {{ user.username }}
    {{ user.password }}
{% endfor %}

Although break and continue are not allowed inside loops, sequences can be filtered.


Here is a small example of a template file example.html.jinja:[11]

<!DOCTYPE html>
    <title>{{ variable|escape }}</title>
  {%- for item in item_list %}
    {{ item }}{% if not loop.last %},{% endif %}
  {%- endfor %}

and templating code:

from jinja2 import Template
with open('example.html.jinja') as f:
    tmpl = Template(f.read())
    variable = 'Value with <unsafe> data',
    item_list = [1, 2, 3, 4, 5, 6]

This produces the HTML string:

<!DOCTYPE html>
    <title>Value with &lt;unsafe&gt; data</title>

Note the minus sign (-) after the tag {%: If you add a minus sign (-) to the start or end of a block (e.g. a For tag), a comment, or a variable expression, the whitespaces before or after that block will be removed.[12]


  1. ^ "Jinja2 Release History". Retrieved 24 June 2020.
  2. ^ "Release 3.1.3". 10 January 2024. Retrieved 19 January 2024.
  3. ^ "Extensions". Jinja2 Documentation (2.8-dev). Retrieved 2015-05-26.
  4. ^ a b c d "Jinja built-in filters and tests (like Django filters)". www.webforefront.com. Retrieved 2023-08-14.
  5. ^ "Extensions". Jinja2 Documentation (2.8-dev). Retrieved 2015-05-26.
  6. ^ DuPlain, R. (2013). Instant Flask Web Development. Packt Publishing. p. 30. ISBN 978-1-78216-963-5. Retrieved 2015-05-26.
  7. ^ "Templating (Jinja2) — Ansible Documentation".
  8. ^ "Understanding Jinja". docs.saltproject.io.
  9. ^ Jinja and macros | dbt Developer Hub
  10. ^ "Welcome | Jinja2 (The Python Template Engine)". palletsprojects.com/p/jinja.
  11. ^ Ronacher, Armin. "Template Designer Documentation". Jinja Documentation (3.0.x). Retrieved 9 January 2024. A Jinja template doesn't need to have a specific extension: .html, .xml, or any other extension is just fine.
  12. ^ "Template Designer Documentation — Jinja Documentation (3.0.x)". jinja.palletsprojects.com. Retrieved 2024-01-09.

External links[edit]