Django SimpleListFilter: ValueError not enough values to unpack (expected 2, got 0)

Question

Context: I'm creating a custom input filter in Django using the SimpleListFilter class. I've followed the steps in here https://hakibenita.com/how-to-add-a-text-filter-to-django-admin, but I'm encountering a ValueError when trying to use the filter. Here is my code:

filters.py:

from django.contrib import admin
from django.db.models import Q

class InputFilter(admin.SimpleListFilter):
title = 'Language'
parameter_name = 'language'
template = 'admin/input_filter.html'

def lookups(self, request, model_admin):
    # Dummy, required to show the filter.
    return ((),)

def queryset(self, request, queryset):
    if self.value():
        return queryset.filter(Q(language__icontains=self.value()))

def choices(self, changelist):
    all_choices = super().choices(changelist)
    query_params = changelist.get_filters_params()
    if not self.lookup_choices:
        return []

    for lookup, title in self.lookup_choices:
        query_parts = changelist.get_query_string({self.parameter_name: lookup}).split('&')
        if query_parts and len(query_parts) >= 2:
            query = '&'.join([f'{k}={v}' for k, v in query_parts])
            choice = {
                'query_string': f'?{query}&{query_params}',
                'display': title,
                'selected': self.value() == lookup,
            }
            all_choices.append(choice)

    return all_choices

I get the following error when accessing the admin page:

ValueError at /repoman/admin/aws_storage/raw_file/ not enough values to unpack (expected 2, got 0)

I'm not sure what is causing this error or how to fix it. Any help would be appreciated!

Traceback:

File "/usr/local/lib/python3.7/site-packages/django/contrib/admin/templatetags/admin_list.py", 
line 440, in admin_list_filter

    'choices': list(spec.choices(cl)),

  File "/app/repoman/aws_storage/filters.py", line 26, in choices
    for lookup, title in self.lookup_choices:
ValueError: not enough values to unpack (expected 2, got 0)

Answer 1

Your lookup is empty. So when it checks with the parameter it gets empty Value. So you should fill up your lookup list.

def lookups(self, request, model_admin):
    return [
      ('en', 'English'),
      ('fr', 'French'),
      ('es', 'Spanish'),
    ]