Jinja2 not returning loop variables

Question

I have a website with Jinja2 on Google App Engine, so the version is 2.6. At some point, I loop through a list to produce radio buttons and I would like to have the first one checked by default. My code is the following:

     {% for publisher in publishers %}
        <tr onclick="doNav('/spt/publisher/{{ publisher.id }}');" style="cursor: pointer;">
            <td>{{ publisher.name }}</td>
            <td>{{ publisher.songs }}</td>
            <td><input form="export_publisher_form" onclick="event.cancelBubble = true;"
                       type="radio" name="export_publisher" value="{{ publisher.id }}"{% if loop.first %} checked{% endif %}></td>
        </tr>
    {% endfor %}

Problem is, Jinja doesn't seem to return any value for loop.first, nor any loop variable (I tried with loop.index, loop.length and loop.cycle). Am I doing something wrong ?

Edit: publishers is a list that looks like this (indented for clarity):

[{'id': 4974053165105152L, 'name': u'BMG', 'songs': 1}, 
 {'id': 5888297083600896L, 'name': u'Emi', 'songs': 2}, 
 {'id': 6099953071947776L, 'name': u'Ninja Tune', 'songs': 1}, 
 {'id': 4762397176758272L, 'name': u'Sony', 'songs': 0}, 
 {'id': 5325347130179584L, 'name': u'Universal', 'songs': 0}, 
 {'id': 4815173734891520L, 'name': u'Warner', 'songs': 0}]

hmmm... don't see anything wrong with the jinja2 code. Can you show the values of publishers? — Andrew Kloos
– Andrew Kloos, Commented Dec 17, 2013 at 21:09
Thanks for replying Andrew. I don't know if you get notified that I edited the question, so I'm replying too. :) — Olivier Le Moign
– Olivier Le Moign, Commented Dec 23, 2013 at 19:13

Andrew Kloos · Accepted Answer · 2013-12-23 22:08:40Z

1

Weird... what version of python are you using? When I execute this code I get the following output:

 {% for publisher in heater %}
    <tr onclick="doNav('/spt/publisher/{{ publisher.id }}');" style="cursor: pointer;">
        <td>{{ publisher.name }}</td>
        <td>{{ publisher.songs }}</td>
        <td><input form="export_publisher_form" onclick="event.cancelBubble = true;"
                   type="radio" name="export_publisher" value="{{ publisher.id }}"{% if loop.index == 2 %} checked{% endif %}></td>
    </tr>
{% endfor %}

I get Emi 2 checked. What are you seeing?

I also changed your data to this:

    data = [{'id': 4974053165105152, 'name': 'BMG', 'songs': 1}, 
              {'id': 5888297083600896, 'name': 'Emi', 'songs': 2}, 
              {'id': 6099953071947776, 'name': 'Ninja Tune', 'songs': 1}, 
              {'id': 4762397176758272, 'name': 'Sony', 'songs': 0}, 
              {'id': 5325347130179584, 'name': 'Universal', 'songs': 0}, 
              {'id': 4815173734891520, 'name': 'Warner', 'songs': 0}]

edited Dec 23, 2013 at 22:08

answered Dec 23, 2013 at 21:56

Andrew Kloos

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4 Comments

Andrew Kloos Over a year ago

Ah - I see you said python 2.6. I retried the code with that version of python and got the same successful results. FYI: I'm testing with cherrypy 3.2.4.

Olivier Le Moign Over a year ago

I'm using Python 2.7. 2.6 is the version of Jinja2 that is supported by GAE.

Olivier Le Moign Over a year ago

It's weird that you're getting Emi checked. It should be the first element. I'll setup a new GAE account to test tomorrow, the problem must be linked to my app, but I have absolutely no idea how.

Andrew Kloos Over a year ago

I used {% if loop.index == 2 %} checked{% endif %} just to check the index was working. You can change that back to loop.first.

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