How to convert dictionary values into list in Python / Django?

Question

In my Django template, I call this frequently:

{% for name, address in directory.addressbook.items %}
  {% for street in address.list %}
    {{street.number}}

How do I create this as a filter? I've tried this, but it doesn't work.

In the template, I call:

{{directory.addressbook.items|all_numbers}}

And in my filter definition I have:

def all_numbers(data):
  number_list=[]
  if isinstance(data, dict):
    for name, address in data:
      for street in data.list():
        number_list.append(street)
    return number_list

But all I get returned is "[ ]". What am I doing wrong?

Not sure if this is part of the problem, but it looks like your outer loop (for name, address in data:) is not getting used at all (you don't use name or address). — SethMMorton
– SethMMorton, Commented Jun 6, 2013 at 0:45
Also, I don't think that dict has a list attribute. This should raise a syntax error. since you aren't seeing that it makes me thing that part of the code isn't being executed. Is data empty? If so, then returning [] is correct. — SethMMorton
– SethMMorton, Commented Jun 6, 2013 at 0:47
ah typo, that was meant to be for street in address.list(). But I don't get an exception there either - whats the right way to do this? (sorry, i'm new to python) — nerdinary
– nerdinary, Commented Jun 6, 2013 at 1:46
Well, street might be an object with a list method, so that might be OK — SethMMorton
– SethMMorton, Commented Jun 6, 2013 at 5:04

Brandon Taylor · Accepted Answer · 2013-06-06 00:48:44Z

1

You need to register your function as a template filter. Also, this code will need to be in a module and then imported into your template as such...

# custom_filters.py
from django import template

register = template.Library()


@register.filter
def all_numbers(data):
  number_list=[]
  if isinstance(data, dict):
    for name, address in data:
      for street in data.list():  # this will raise an exception
        number_list.append(street)
    return number_list

# your-template.html
{% load custom_filters %}

{{ directory.addressbook.items|all_numbers }}

answered Jun 6, 2013 at 0:48

Brandon Taylor

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1 Comment

nerdinary Over a year ago

The function is already registered as a filter, else it would raise an exception when I try to call it. I have plenty of other filters that I'm using. Why would "for street in data.list()" raise an exception?

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