Django Web Framework Tutorials

Resolving “Django Reverse with arguments ‘()’ and keyword arguments ‘{}’ not found”

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Django‘s reverse() function is incredibly useful for programmatically generating URLs in your views and templates. However, you may sometimes run into the frustrating error “Reverse with arguments ‘()’ and keyword arguments ‘{}’ not found”. In this blog post, I’ll explain what’s causing this error and show you exactly how to fix it.

Understanding Django’s Reverse Function

First, let’s briefly review what Django’sReverse() function does. TheReverse() function translates a URL name (and optionally arguments and keyword arguments) into a actual URL path. For example:

from django.urls import reverse

reverse('product-detail', args=[123])
# Returns: '/products/123/'

This saves you from having to hardcode URLs across your project. Instead, you define a name for each URL pattern, whichReverse() then maps to the actual URL.

When the Reverse Error Occurs

The “Reverse with arguments…’ not found” error happens when you try to reverse a URL but pass arguments or keyword arguments that don’t line up with what’s defined in your urls.py file.

For example, this product URL requires a product ID argument:

# urls.py

path('products/<int:product_id>/', views.product_detail, name='product-detail')

If you try toReverse it without passing a product ID or passing an invalid argument, you’ll get theReverse error:

reverse('product-detail') # Fails - no arguments

reverse('product-detail', args=['iphone']) # Fails - string instead of integer

So the key is making sure your arguments match what the URL pattern is expecting.

Fixing the Reverse Error

Here are the steps to fix a “Reverse with arguments not found” error:

1. Inspect Your urls.py File

Examine the url pattern that’s causing issues and identify exactly what arguments/keyword arguments it requires.

2. Pass the Correct Arguments to reverse()

Make sure you’re passing arguments that match the url pattern’s requirements. Common issues:

  • Forgetting required arguments
  • Passing positional instead of keyword args
  • Passing strings instead of integers

3. Define URL Name Spaces

If you have multiple urls.py files, make sure you’ve defined app namespaces and are including them when reversing.
For example:

# urls.py 

app_name = 'products'

# views.py

reverse('products:product-detail', args=[123])

This helps Django match the name to the correct file.

Example Fix

Here’s an example fix for a common case of forgetting required ID arguments:
Incorrect

# urls.py 

path('bands/<int:band_id>/', views.band_detail, name='band-detail')

# views.py

reverse('band-detail') # Error!

Correct Fix

# urls.py
# Same pattern

# views.py 

reverse('band-detail', args=[311]) # Works!

Key Takeaways

  • TheReverse error happens when arguments don’t match the url pattern
  • Inspect your URLs to identify expected args
  • Pass the right arguments and namespaces toReverse()
  • Arguments must be positional args first, then keyword args

Carefully checking required arguments and namespaces will save you many headaches! Let me know in the comments if you have any other reverse() tips.