Jinja2 shorthand conditional

Question

Say I have this:

{% if files %}
    Update
{% else %}
    Continue
{% endif %}

In PHP, say, I can write a shorthand conditional, like:

<?php echo $foo ? 'yes' : 'no'; ?>

Is there then a way I can translate this to work in a jinja2 template:

'yes' if foo else 'no'

I don't know if this helps, but the php expression looks a lot like what is called the "ternary operator" in C-like languages. The final line is called the "conditional expression" in python, although I've seen it called the ternary operator in python as well. Anyway, I mention it as it might help to know the names of those things in a google search. — mgilson, Jan 08 '13 at 12:30

score 531 · Accepted Answer · answered Jan 08 '13 at 12:32

531

Yes, it's possible to use inline if-expressions:

{{ 'Update' if files else 'Continue' }}

answered Jan 08 '13 at 12:32

bereal

96

A shorthand for `{{ value if value else 'No value' }}` would be `{{ value or 'No value' }}` – Don Grem Dec 30 '14 at 11:39
16

@DorinGrecu My code is not full with `{{ tobe or 'Not to be' }}` thanks to you :) – dcohenb Mar 15 '16 at 10:40
22

If you need to use a variable, you can use inside `{% %}` too. Like `{% set your_var = 'Update' if files else 'Continue' %}` – jhpg Jun 25 '17 at 20:43
can it also contain markup like: {{ '
Update
' if files else '
Continue
' }}? – Macilias Feb 09 '22 at 14:03
1

@Macilias depends on how `autoescape` is configured. If it's set to `True`, you may need to add the `| safe` filter. – bereal Feb 09 '22 at 14:11
What to do in following condition `{{ "Whoops" if message.tags == 'danger' else message.tags }}` – TarangP Apr 26 '22 at 12:58

score 11 · Answer 2 · answered Nov 20 '19 at 12:13

11

Alternative way (but it's not python style. It's JS style)

{{ files and 'Update' or 'Continue' }}

answered Nov 20 '19 at 12:13

user3713526

2

This construct is not really applicable in languages that interpret an empty string as falsy. `True and '' or 'a'` will evaluate to `a`, which is not what was intended. – Gabriel Jablonski Jan 11 '20 at 09:12

2 Answers2