How to use django template dot notation inside a for loop

Question

I am trying to retrieve the value of a dictionary key and display that on the page in a Django template:

{% for dictkey in keys %} <p> {{ mydict.dictkey }} </p> {% endfor %}

(let's say 'keys' and 'mydict' have been passed into the template in the Context)

Django renders the page but without the dictionary contents ("Invalid template variable")

I assume the problem is that it is trying to do mydict['dictkey'] instead of mydict[actual key IN the variable dictkey]? How does one "escape" this behavior?

Thanks!

UPDATE: Based on the answers received, I need to add that I'm actually looking specifically for how to achieve a key lookup inside a for loop. This is more representative of my actual code:

{% for key, value in mydict1.items %} <p> {{ mydict2.key }} </p> {% endfor %}

Basically, I have two dictionaries that share the same keys, so I can't do the items() trick for the second one.

The less fancy logic in the template the better. Try and prepare the data in an easily templatable fashion before passing it to be rendered. — kevpie
– kevpie, Commented Dec 6, 2010 at 4:38

Community · Accepted Answer · 2017-05-23 12:26:54Z

4

See this answer to a (possibly duplicate) related question.

It creates a custom filter that, when applied to a dictionary with a key as it's argument, does the lookup on the dictionary using the key and returns the result.

Code:

@register.filter def lookup(d, key): if key not in d: return None return d[key]

Usage:

{% for dictkey in dict1.keys %} <p> {{ dict2|lookup:dictkey }} </p> {% endfor %}

Registering the filter is covered in the documentation.

I find it sad that this sort of thing isn't built in.

edited May 23, 2017 at 12:26

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answered Dec 6, 2010 at 4:03

Cameron

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6 Comments

mindthief Over a year ago

@Cameron: nice, that looks like it'll do what I want! Thanks! But yea shouldn't have to use a custom filter like this for something so simple. At least I now know about custom filters :)

Cameron Over a year ago

@mindthief: Glad to have helped. If the limitations intentionally imposed in Django templates start to get to you too much, you might want to consider switching to another templating language -- Jinja2 is excellent and has similar syntax but many more features (including dictionary lookups!)

mindthief Over a year ago

Thanks for the tips! So I'm having a little trouble getting the custom filter to work atm -- I put it in a file myextras.py which is located in the same folder as the django project. Added {% load myextras %} at the top of the template.html file, and the file contains the code you provided (@register filter def lookup...). I also added 'from django import template' and 'register = template.Library()' to this file to see if that would work, but I still get the error message "myextras is not a valid tag library: Template library myextras not found, tried django.templatetags.myextras". Any ideas?

Cameron Over a year ago

@mindthief: Sounds like Django can't find myextras (your code seems correct). Is myextras.py in the templatetags directory? Is there an empty __init__.py file in the directory? Make sure your directory is set up exactly as per the instructions

mindthief Over a year ago

@Cameron: Yes, that was it! Ugh, I was hesitant to add a new app just to get the filter to work, so I had tried to just put the templatetags/ folder in the main django project folder (didn't have any apps in this project). I figured that it should be able to find it in that folder just the same as if it were in an "installed app", but apparently not. I tried that now and it worked -- that is, I did 'python manage.py startapp extras'. And then copied templatetags/ into that folder, added 'myproj.extras' to INSTALLED_APPS in settings.py, and that did it. Really appreciate the assistance! :)

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Chris Morgan · Accepted Answer · 2010-12-06 03:52:45Z

From http://docs.djangoproject.com/en/dev/ref/templates/builtins/#for

This can also be useful if you need to access the items in a dictionary. For example, if your context contained a dictionary data, the following would display the keys and values of the dictionary:

{% for key, value in data.items %} {{ key }}: {{ value }} {% endfor %}

The trick is that you need to call dict.items() to get the (key, value) pair.

I actually did do that, but for another dict. The problem I guess is that I actually have two dictionaries that share the same keys. One of them is in the for loop as: for key, value in myDict1.items: <p> {{ myDict2.key }} </p>

Adam Vandenberg · Accepted Answer · 2010-12-06 03:53:16Z

See the docs: http://docs.djangoproject.com/en/dev/ref/templates/builtins/#for

{% for key, value in data.items %} {{ key }}: {{ value }} {% endfor %}

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