URLs and Routing

Introduction

Django maps incoming URL paths to Python callables through URLconf modules—Python lists of path() (or re_path()) entries. This chapter builds on the blog/urls.py wiring from chapter 03: path converters, include(), named URLs, reverse(), and RESTful routing conventions that reappear in class-based views and Django REST Framework.

Prerequisites

• Your First Django Project — blog app with root home view
• Project Structure — know config/urls.py vs blog/urls.py

URLconf Basics

Root vs app URLconfs

config/urls.py (project root):

from django.contrib import admin
from django.urls import include, path
 
urlpatterns = [
    path("admin/", admin.site.urls),
    path("", include("blog.urls")),
    path("blog/", include("blog.urls")),  # optional prefix — pick one pattern
]

blog/urls.py (app):

from django.urls import path
 
from . import views
 
urlpatterns = [
    path("", views.home, name="home"),
    path("posts/", views.post_list, name="post-list"),
    path("posts/<int:pk>/", views.post_detail, name="post-detail"),
]

If mounted at path("blog/", include("blog.urls")), the list URL is /blog/posts/.

path() signature

path(route, view, kwargs=None, name=None)

Path Converters

Capture part of the URL and pass it as a view argument:

Examples:

path("posts/<int:pk>/", views.post_detail),
path("category/<slug:slug>/", views.category),
path("files/<path:filepath>/", views.serve_file),

blog/views.py (stubs for routing practice):

Code explanation:

• pk in the path becomes post_detail(request, pk=1) for /posts/1/
• Converter name in angle brackets must match the view parameter name

include() for App Routes

path("api/", include("blog.urls")),
path("accounts/", include("django.contrib.auth.urls")),

Benefits:

• Each app owns its urls.py
• Reusable apps ship URLconf you mount once
• Root file stays small

Namespaces (optional)

When the same app is included twice or you need disambiguation:

# config/urls.py
path("blog/", include(("blog.urls", "blog"), namespace="blog")),

Template: {% url 'blog:post-detail' pk=1 %}. Use when docs or third-party apps require it; simple projects often skip namespaces.

re_path() (Regular Expressions)

Legacy and edge cases:

from django.urls import re_path
 
re_path(r"^posts/(?P<year>[0-9]{4})/$", views.posts_by_year),

Prefer path() with converters for readability. Use re_path() when patterns do not fit converters.

Named URLs and Reverse Resolution

name= in path()

path("posts/<int:pk>/", views.post_detail, name="post-detail"),

reverse() in Python

from django.shortcuts import redirect
from django.urls import reverse
 
def some_view(request):
    url = reverse("post-detail", args=[42])
    # '/posts/42/' or '/blog/posts/42/' depending on mount
    return redirect("post-detail", pk=42)  # shortcut

redirect() shortcuts

return redirect("home")
return redirect("post-detail", pk=1)
return redirect("/hard-coded/")  # avoid when possible

Hard-coded paths break when URL structure changes; named URLs stay stable.

Templates (preview)

In templates (covered in chapter 08):

<a href="{% url 'post-detail' pk=post.id %}">Read more</a>

Requires name="post-detail" on the path.

Query Strings vs Path Parameters

Path: /posts/5/ → view arg pk=5

Query: /posts/?page=2&tag=django → request.GET

def post_list(request):
    page = request.GET.get("page", "1")
    tag = request.GET.get("tag")
    ...

Use path segments for resource identity; query strings for filters, pagination, optional params.

RESTful Routing Conventions

Conceptual map (full CRUD in views chapter):

Django URLconf only maps path + view; HTTP method dispatch happens in the view (@require_http_methods, CBV, or DRF). Same path, different methods:

@require_http_methods(["GET", "POST"])
def post_list(request):
    if request.method == "GET":
        ...
    elif request.method == "POST":
        ...

DRF ViewSets and routers automate this table—chapter 19.

Trailing Slashes

Django APPEND_SLASH (default True) redirects /posts → /posts/ when a trailing-slash pattern exists.

Convention: define patterns with trailing slash:

path("posts/", views.post_list),  # preferred

Compare: Spring MVC routing uses different path rules—Django’s slash behavior is easy to miss in API-only apps (APPEND_SLASH=False sometimes used for REST).

Debugging URL Issues

python manage.py show_urls

If django-extensions is not installed, inspect manually or add temporary logging:

# config/urls.py — dev only
from django.urls import get_resolver
print(get_resolver().url_patterns)

Common errors:

Full Example: blog/urls.py

from django.urls import path
 
from . import views
 
urlpatterns = [
    path("", views.home, name="home"),
    path("posts/", views.post_list, name="post-list"),
    path("posts/new/", views.post_create, name="post-create"),
    path("posts/<int:pk>/", views.post_detail, name="post-detail"),
    path("posts/<int:pk>/edit/", views.post_edit, name="post-edit"),
    path("category/<slug:slug>/", views.category, name="category"),
]

config/urls.py:

urlpatterns = [
    path("admin/", admin.site.urls),
    path("", include("blog.urls")),
]

Test:

python manage.py runserver
curl http://127.0.0.1:8000/posts/1/

Post-Chapter Checklist

• You can add path() entries with int and slug converters
• You use include("blog.urls") from the project root
• You assign name= and use reverse() / redirect()
• You distinguish path args from request.GET
• You know RESTful path naming for later CRUD chapters

FAQ

path() vs url()?

url() was removed in Django 4+—use path() / re_path().

API without trailing slash?

Set APPEND_SLASH = False in settings and define patterns consistently; document for API clients.

Multiple parameters?

path("archive/<int:year>/<int:month>/", views.archive),

View: def archive(request, year, month):

External link in {% url %}?

{% url %} is for internal routes only. Use plain href="https://...".

Same name in two apps?

Use namespaces or unique names like blog-post-detail vs shop-item-detail.