Django: jinja2 code not working when iterated over the same list twice

Question

I have an html file in my django project as follows:

<body>
<div class="row">
    <div class="col-sm-3">
            <ul class="list-group">
                {% for image in images %}
                <li class="list-group-item">{{ image.name}}
                <img class="img-responsive" src='http://krishna.com{{ image.path }}' />
                </li>
                {% endfor %}
            </ul>
    </div>
    <div class="col-sm-9">
            <ul class="list-group">
                {% for image in images %}
                <li class="list-group-item">{{ image.name}}
                <img class="img-responsive" src='http://krishna.com{{ image.path }}' />
                </li>
                {% endfor %}
            </ul>
    </div>
</div>
</body>

the content is showing for the <div class="col-sm-3">

but no content is being shown for <div class="col-sm-9">

In the image below, even thought the jinja code is same for both the divs, it shows only on one side.

One may ask why i am doing. I am just testing.

Edit:

I am generating the list in the following way:

def gallery(request):
    import os, sys
    img_list = os.scandir('/home/shared/pictures')
    return render(request,'blog/gallery.html', {'images': img_list})

images is an array of file names. check the edited question with the image — Santhosh, Sep 13 '16 at 06:22
I found only one similar question. but couldnt find an answer in it, http://stackoverflow.com/questions/13651965/iterate-over-the-same-list-twice-in-jinja2 — Santhosh, Sep 13 '16 at 07:07

score 1 · Accepted Answer · edited May 23 '17 at 11:51

1

You might be passing a generator object instead of a list / tuple.

The difference is that you can iterate over the generator object only once.

For example (below is the last / equivalent line in your view that renders the template)

return render(request, "template.html", {'images': (i for i in range(10))})

Will result in images being iterated over only once. (In your example, the col-sm-9 block will be empty).

If you need to iterate over something more than once, you must pass it as a list or tuple.

return render(request, "template.html", {'images': list(i for i in range(10))})

edited May 23 '17 at 11:51

Community

1
1

answered Sep 13 '16 at 07:09

Kedar

1,343
8
17

so in my case. (see the edited question) i am getting a list of files from a directory. So how to make it a list – Santhosh Sep 13 '16 at 07:14
Try `{'images': list(img_list)}` – Kedar Sep 13 '16 at 08:54
If you see img_list has a path and name for each item. If i try that, it will only show me the path – Santhosh Sep 13 '16 at 09:17
That is not true, calling list doesn't change the structure of the items in your iterable. – Kedar Sep 14 '16 at 03:49

Django: jinja2 code not working when iterated over the same list twice

1 Answers1