Use variable as dictionary key in Django template

Question

I'd like to use a variable as an key in a dictionary in a Django template. I can't for the life of me figure out how to do it. If I have a product with a name or ID field, and ratings dictionary with indices of the product IDs, I'd like to be able to say:

{% for product in product_list %}
     <h1>{{ ratings.product.id }}</h1>
{% endfor %}

In python this would be accomplished with a simple

ratings[product.id]

But I can't make it work in the templates. I've tried using with... no dice. Ideas?

possible duplicate of [how to access dictionary element in django template?](http://stackoverflow.com/questions/1275735/how-to-access-dictionary-element-in-django-template) — Anto, Feb 17 '14 at 15:31

score 103 · Answer 1 · answered May 22 '12 at 10:23

103

Create a template tag like this (in yourproject/templatetags):

@register.filter
def keyvalue(dict, key):    
    return dict[key]

Usage:

{{dictionary|keyvalue:key_variable}}

answered May 22 '12 at 10:23

Thorin Schiffer

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2

You also need a bunch of peripheral stuff to make this work so make sure you check out the documentation: https://docs.djangoproject.com/en/dev/howto/custom-template-tags/ – Chase Roberts Jun 12 '13 at 04:01
2

Can this be chained for nested dicts? Something like `{{dictionary|keyvalue:key_variable|keyvalue:another_key}}` ? – Petr Peller Nov 03 '13 at 20:59
Theoretically yes, try it out ;) – Thorin Schiffer Nov 04 '13 at 10:07
4

This is such a trivial thing. Why doesn't django support this out of the box? – Y M Jun 13 '18 at 02:51
1

@mango because they want to stay away from `logic` in templates and encourage putting it in the view – Anupam Jun 29 '18 at 10:39
Need to add more descriptions – Aravind Srinivas Oct 24 '18 at 10:22

score 23 · Accepted Answer · answered May 24 '10 at 02:13

23

You need to prepare your data beforehand, in this case you should pass list of two-tuples to your template:

{% for product, rating in product_list %}
    <h1>{{ product.name }}</h1><p>{{ rating }}</p>
{% endfor %}

answered May 24 '10 at 02:13

cji

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Thanks cji! I was trying to avoid another object, but it doesn't really matter... it's all cached anyway. – CaptainThrowup May 24 '10 at 03:57
3

You don't need to prep the data in the view, you can achieve the same thing by calling `items` on the dictionary that's already in the context -- `{% for product, rating in product_list.items %}` will work. – jhrr Feb 24 '17 at 20:36

score 15 · Answer 3 · answered Dec 29 '12 at 01:31

15

There is a very dirty solution:

<div>We need d[{{ k }}]</div>

<div>So here it is:
{% for key, value in d.items %}
    {% if k == key %}
        {{ value }}
    {% endif %}
{% endfor %}
</div>

answered Dec 29 '12 at 01:31

podshumok

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score 15 · Answer 4 · answered Jul 02 '14 at 02:28

15

Building on eviltnan's answer, his filter will raise an exception if key isn't a key of dict.

Filters should never raise exceptions, but should fail gracefully. This is a more robust/complete answer:

@register.filter
def keyvalue(dict, key):    
    try:
        return dict[key]
    except KeyError:
        return ''

Basically, this would do the same as dict.get(key, '') in Python code, and could also be written that way if you don't want to include the try/except block, although it is more explicit.

answered Jul 02 '14 at 02:28

Patrick

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instead of dict[key] you just use the built-in python dictionary get method. e.g.: return dict.get(key, '') – user772401 Sep 29 '14 at 01:33
2

You should also catch a potential TypeError. Parameter "dict" is not guaranteed to be a Python dict. – jrief Jun 11 '18 at 10:18

Use variable as dictionary key in Django template

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