.items not working on defaultdict in Django template

Question

I can't get .items to work in my Django template:

copy and paste from my CBV's get_context_data:

    context['data'] = assertion_dict
    context['dataitems'] = assertion_dict.items()

    return context

copy and paste from my template:

  <h3>data dump</h3>
  {{data}}

  <h3>dataitems</h3>
  {% for key, value in dataitems %}
     {{ key }}: {{ value }} <br/>
  {% endfor %}

  <h3>data.items</h3>
  {% for key, value in data.items %}
     {{ key }}: {{ value }} <br/>
  {% endfor %}

  <h3>Not found test</h3>
  {{ i_dont_exist }}

output:

**data dump**
defaultdict(<class 'list'>, {<BadgeType: Talent>: [<BadgeAssertion: Blender Blue Belt>], <BadgeType: Achievement>: [<BadgeAssertion: MyBadge#1>, <BadgeAssertion: MyBadge#1>, <BadgeAssertion: MyBadge#2>], <BadgeType: Award>: [<BadgeAssertion: Copy of Copy of Blenbade>]})

**dataitems**
Talent: [<BadgeAssertion: Blender Blue Belt>]
Achievement: [<BadgeAssertion: MyBadge#1>, <BadgeAssertion: MyBadge#1>, <BadgeAssertion: MyBadge#2>]
Award: [<BadgeAssertion: Copy of Copy of Blenbade>]

**data.items**

**Not found test**
DEBUG WARNING: undefined template variable [i_dont_exist] not found

Why isn't the second version working, where I use data.items in my template?

There's nothing obviously wrong with your first example template. Check for typos or accidental reassignment of `context['data']` or deletion of items from `assertion_dict`. — Peter DeGlopper, Sep 27 '15 at 23:33
To rule out typos and other problems, I sent both in the context at the same time, and copy/pasted the view, template, and resulting HTML output. Question is updated with this info. — 43Tesseracts, Sep 28 '15 at 01:42
I would a) add a dump of `{{ data }}` somewhere in your template - Python dicts stringify in a reasonable way, and that should help verify whether or not your `data` variable contains what you expect - and b) temporarily set your `TEMPLATE_STRING_IF_INVALID` setting as described here: http://stackoverflow.com/a/8990344/2337736 — Peter DeGlopper, Sep 28 '15 at 02:33

score 9 · Accepted Answer · answered Sep 28 '15 at 04:46

This is a known issue in Django: you cannot iterate over a defaultdict in a template. The docs suggest that the best way to handle this is to convert your defaultdict to a dict before passing it to the template:

context['data'] = dict(assertion_dict)

The reason it doesn't work, by the way, is that when you call {{ data.items }} in your template, Django will first attempt to find data['items'], and then data.items. The defaultdict will return a default value for the former, so Django will not attempt the latter, and you end up trying to loop over the default value instead of the dict.

.items not working on defaultdict in Django template

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