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2. RegEx in URL

Django provides re_path() (regular expression-based path matching) as an alternative to path(), allowing more complex URL patterns.

1. When to Use re_path

You should use re_path() when:

  • You need flexible URL patterns (e.g., support multiple formats).
  • You require complex validation (e.g., specific ID ranges).
  • path() is too simple for your needs.

2. Basic Example of re_path

Instead of using path(), we use re_path() from django.urls and match the URL using a regular expression.

Example: Using re_path for Book Details

urls.py

from django.urls import re_path
from . import views


urlpatterns = [
    re_path(r'^book/(?P<book_id>\d+)/$', views.book_detail, name='book_detail'),
]

✔ Regex Explanation (r'^book/(?P<book_id>\d+)/$'):

  • ^book/ → URL must start with "book/"
  • (?P<book_id>\d+) → Captures numbers (\d+), named as book_id
  • /$ → Ensures the URL ends with /

views.py

from django.http import HttpResponse


def book_detail(request, book_id):
    return HttpResponse(f"Book ID: {book_id}")

✅ Example URLs that match:

  • http://127.0.0.1:8000/book/1/
  • http://127.0.0.1:8000/book/123/

🚫 Examples that don’t match:

  • http://127.0.0.1:8000/book/abc/ (only digits are allowed)
  • http://127.0.0.1:8000/book/12 (missing / at the end)

3. Using re_path for Slugs

If you need to capture both numbers and letters, use a slug-based regex.

urls.py

urlpatterns = [
    re_path(r'^book/(?P<book_slug>[\w-]+)/$', views.book_detail_by_slug, name='book_detail_by_slug'),
]

✔ Regex Explanation (r'^book/(?P<book_slug>[\w-]+)/$'):

  • [\w-]+ → Matches letters, numbers, and dashes (-)
  • Named capture (?P<book_slug>...) makes it accessible in views

views.py

def book_detail_by_slug(request, book_slug):
    return HttpResponse(f"Book Slug: {book_slug}")

✅ Example URLs that match:

  • http://127.0.0.1:8000/book/django-basics/
  • http://127.0.0.1:8000/book/python-tips/

4. Using Multiple Patterns in One re_path

You can combine multiple patterns into a single re_path().

Example: Match ID or Slug

urlpatterns = [
    re_path(r'^book/(?P<book_param>\d+|[\w-]+)/$', views.book_detail_mixed, name='book_detail_mixed'),
]

views.py

def book_detail_mixed(request, book_param):
    return HttpResponse(f"Book ID or Slug: {book_param}")

✅ Matches both IDs and slugs:

  • http://127.0.0.1:8000/book/123/
  • http://127.0.0.1:8000/book/django-for-beginners/

5. Should You Use re_path or path?

Featurepath()re_path()
Simple, readable✅ Yes❌ No (uses regex)
Best for numeric IDs✅ Yes (<int:id> is simple)✅ Yes
Allows complex patterns❌ No✅ Yes (e.g., \d+ or [\w-]+)
Supports optional parts❌ No✅ Yes (with ?)
Recommended for most cases✅ Yes❌ No (use only if needed)

🚀 Best Practice: Use path() unless you need advanced regex features.

6. When to Use re_path?

Use re_path() if: ✅ You need optional URL parameters (?).
✅ You want to match multiple patterns in one rule.
✅ You need custom validation beyond Django’s built-in converters.

Otherwise, stick with path() for better readability.