Use QueryDict for default data.

django_filters/filterset.py

@@ -7,7 +7,7 @@
 from django.db import models
 from django.db.models.constants import LOOKUP_SEP
 from django.db.models.fields.related import ManyToManyRel, ManyToOneRel, OneToOneRel
-from django.utils.datastructures import MultiValueDict
+from django.http import QueryDict
 
 from .conf import settings
 from .constants import ALL_FIELDS
@@ -192,7 +192,7 @@ def __init__(self, data=None, queryset=None, *, request=None, prefix=None):
         model = queryset.model
 
         self.is_bound = data is not None
-        self.data = data or MultiValueDict()
+        self.data = data or QueryDict()
         self.queryset = queryset
         self.request = request
         self.form_prefix = prefix

django_filters/widgets.py

@@ -6,9 +6,9 @@
 from django import forms
 from django.db.models.fields import BLANK_CHOICE_DASH
 from django.forms.utils import flatatt
-from django.http import QueryDict
 from django.utils.datastructures import MultiValueDict
 from django.utils.encoding import force_str
+from django.utils.http import urlencode
 from django.utils.safestring import mark_safe
 from django.utils.translation import gettext as _
 
@@ -56,13 +56,13 @@ def render_option(self, name, selected_choices, option_value, option_label):
         option_value = force_str(option_value)
         if option_label == BLANK_CHOICE_DASH[0][1]:
             option_label = _("All")
-
-        data = QueryDict(mutable=True)
-        data.update(self.data)
+        data = self.data.copy()
         data[name] = option_value
-
         selected = data == self.data or option_value in selected_choices
-        url = data.urlencode()
+        try:
+            url = data.urlencode()
+        except AttributeError:
+            url = urlencode(data)
         return self.option_string() % {
             "attrs": selected and ' class="selected"' or "",
             "query_string": url,

tests/test_widgets.py

@@ -1,6 +1,6 @@
 from django.forms import NumberInput, Select, TextInput
 from django.test import TestCase
-from django.utils.datastructures import MultiValueDict
+from django.http import QueryDict
 from django_filters.widgets import (
     BaseCSVWidget,
     BooleanWidget,
@@ -143,15 +143,15 @@ def test_widget_with_blank_choice(self):
             </ul>""",
         )
 
-    def test_widget_multivaluedict(self):
+    def test_widget_with_empty_querydict(self):
         choices = (
             ("", "---------"),
             ("test-val1", "test-label1"),
             ("test-val2", "test-label2"),
         )
 
         w = LinkWidget(choices=choices)
-        w.value_from_datadict(MultiValueDict(), {}, "price")
+        w.value_from_datadict(QueryDict(), {}, "price")
         self.assertHTMLEqual(
             w.render("price", ""),
             """