[Python] Django Admin Theme Switching Between Grappelli and Jazzmin Not Working (Session-Based)

Problem Statement:


I am working on a Django e-commerce project and want users to switch between two admin themes: Grappelli and Jazzmin using Django sessions.

I have implemented a session-based theme switcher, but:

• The admin panel always loads Grappelli by default.
• The switch button appears, but clicking it does not apply the correct theme.
• After switching to Jazzmin, I get a "Page Not Found" error (404).

Project Setup

1. Installed Apps (settings.py)


INSTALLED_APPS = [
"grappelli", # Defaulting to Grappelli
"jazzmin", # Want to switch between these two

"colorfield",
"core.apps.CoreConfig", # My core app
"django.contrib.admin",
"django.contrib.auth",
"django.contrib.contenttypes",
"django.contrib.sessions",
"django.contrib.messages",
"django.contrib.staticfiles",
"django.contrib.humanize",
]


Grappelli is loading by default, even when the session should switch to Jazzmin.

2. Middleware for Dynamic Theme Switching (core/middleware.py)


from django.utils.deprecation import MiddlewareMixin

class DynamicAdminThemeMiddleware(MiddlewareMixin):
def process_request(self, request):
from django.conf import settings

if request.session.get("admin_theme") == "grappelli":
settings.INSTALLED_APPS = ["grappelli"] + [app for app in settings.INSTALLED_APPS if app != "jazzmin"]
else:
settings.INSTALLED_APPS = ["jazzmin"] + [app for app in settings.INSTALLED_APPS if app != "grappelli"]


I suspect modifying settings.INSTALLED_APPS dynamically might not be effective.
Does Django require a restart for INSTALLED_APPS changes to take effect?

Middleware is included in settings.py:

MIDDLEWARE = [
"django.middleware.security.SecurityMiddleware",
"django.contrib.sessions.middleware.SessionMiddleware",
"core.middleware.DynamicAdminThemeMiddleware", # Custom middleware
"django.middleware.common.CommonMiddleware",
"django.middleware.csrf.CsrfViewMiddleware",
"django.contrib.auth.middleware.AuthenticationMiddleware",
"django.contrib.messages.middleware.MessageMiddleware",
"django.middleware.clickjacking.XFrameOptionsMiddleware",
]

3. URL Configuration (core/urls.py)


from django.urls import path
from core.views import switch_theme

urlpatterns = [
path("switch_theme/", switch_theme, name="switch_theme"), # Theme switcher
]


Did I miss something in the URL configuration?

4. Theme Switching View (core/views.py)


from django.shortcuts import redirect

def switch_theme(request):
current_theme = request.session.get("admin_theme", "jazzmin")

if current_theme == "grappelli":
# Switch to Jazzmin – redirect to /admin/
request.session["admin_theme"] = "jazzmin"
request.session.modified = True # Ensure session updates
return redirect("/admin/") # Redirect to Django admin

else:
# Switch to Grappelli – redirect to /grappelli/
request.session["admin_theme"] = "grappelli"
request.session.modified = True # Ensure session updates
return redirect("/grappelli/")


The session updates, but the theme doesn't switch correctly.
Is the middleware overriding session-based theme switching?

Main Project urls.py


from django.contrib import admin
from django.urls import path, include

urlpatterns = [
path('grappelli/', include('grappelli.urls')),
path('admin/', admin.site.urls),
path("", include("core.urls")),
]

5. Admin Template Modification (templates/admin/base_site.html)


{% extends "admin/base.html" %}

{% block branding %}
<h1>My Custom Admin Panel</h1>
{% endblock %}

{% block userlinks %}
{{ block.super }}

<p>DEBUG: Admin Theme is: {{ request.session.admin_theme }}</p>

{% if request.session.admin_theme == "grappelli" %}
<a href="{% url 'core:switch_theme' %}">Switch to Jazzmin</a>
{% else %}
<a href="{% url 'core:switch_theme' %}">Switch to Grappelli</a>
{% endif %}
{% endblock %}


The switcher appears, but the session is not applied correctly.
Is there an issue with how I'm referencing request.session.admin_theme?

Issue I Am Facing

1. Theme Always Loads as Grappelli
   • Even when the session should switch to Jazzmin.
2. Clicking "Switch Theme" Redirects to a 404 Page
   • /admin/ is not loading Jazzmin properly.
3. Switching Doesn't Persist
   • Even though request.session["admin_theme"] changes, the applied theme does not.

What I Have Tried

• Restarted Django server after modifying settings:
  python manage.py runserver
• Cleared browser cache and cookies to ensure sessions refresh.
• Checked session updates by printing request.session.admin_theme.
• Tried different redirect URLs (reverse("admin:index") instead of /admin/).
• Verified INSTALLED_APPS order and middleware execution.

Questions

1. Can INSTALLED_APPS be modified dynamically in middleware, or does Django require a restart?
2. Why is Jazzmin giving a 404 error when switching?
3. Is there a better way to apply admin themes dynamically using sessions?

System Information

• Django Version: 5.1.3
• Python Version: 3.12.5
• Jazzmin Version: 3.0.1
• Grappelli Version: 4.0.1
• Database: SQLite

Expected Behavior

• /admin/ should load Jazzmin.
• /grappelli/ should load Grappelli.
• Clicking Switch Theme should apply the correct theme without errors.

**Any help would be greatly appreciated! Thanks in advance! **

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