How to access list using variable indexes in Django templates

djangodjango-templates

Say, I have two lists of objects, foo and bar. In a Django template, while looping through foo, there's a counter that keeps track of the current index/iteration and the counter is used to access bar. The problem here is I don't think Django template system supports accessing list using variable indexes. Is that true? If so, is there any workaround for the problem (other than repeating the same piece of html/template code with hard-coded indexes)?

Code demonstration:

{% for x in foo %}
  <span>{{ x.name }} vs. {{ bar.{{ forloop.counter0 }}.name }}</span>
{% endfor %}

Django template doesn't like {{ bar.{{ forloop.counter0 }}.name }}

Note: I am using Django 1.4

Best Answer

You are correct that Django templates do not directly allow this, and it's because Django tries to force you to put pretty much all your presentation logic in your views. Your best option is to make a list of dicts in your context in your view, so you can iterate of that and access the members by name. Or:

zip your lists together instead of making them a dict and access them using {% for fooItem, barItem in zippedList %}.
use a less limiting templating language, like Jinja2
use a custom template filter, as suggested by Yuji Tomita

Related Solutions

Access constants in settings.py from templates in Django

If it's a value you'd like to have for every request & template, using a context processor is more appropriate.

Here's how:

Make a context_processors.py file in your app directory. Let's say I want to have the ADMIN_PREFIX_VALUE value in every context:

from django.conf import settings # import the settings file

def admin_media(request):
    # return the value you want as a dictionnary. you may add multiple values in there.
    return {'ADMIN_MEDIA_URL': settings.ADMIN_MEDIA_PREFIX}

add your context processor to your settings.py file:

TEMPLATES = [{
    # whatever comes before
    'OPTIONS': {
        'context_processors': [
            # whatever comes before
            "your_app.context_processors.admin_media",
        ],
    }
}]

Use RequestContext in your view to add your context processors in your template. The render shortcut does this automatically:
```
from django.shortcuts import render

def my_view(request):
    return render(request, "index.html")
```

and finally, in your template:

...
<a href="{{ ADMIN_MEDIA_URL }}">path to admin media</a>
...

Python – How to do a not equal in Django queryset filtering

You can use Q objects for this. They can be negated with the ~ operator and combined much like normal Python expressions:

from myapp.models import Entry
from django.db.models import Q

Entry.objects.filter(~Q(id=3))

will return all entries except the one(s) with 3 as their ID:

[<Entry: Entry object>, <Entry: Entry object>, <Entry: Entry object>, ...]

Best Answer

Related Solutions

Access constants in settings.py from templates in Django

Python – How to do a not equal in Django queryset filtering

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