URL parameter type converters in Django - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this Django URL pattern matching?

Given the URL pattern and view below, what will be the value of year inside the view when the URL /archive/2023/ is accessed?

Django

from django.urls import path
from django.http import HttpResponse

def archive_view(request, year):
    return HttpResponse(f"Year: {year}")

urlpatterns = [
    path('archive/<int:year>/', archive_view),
]

A "Year: 2023"

B "Year: '2023'" (string with quotes)

C "Year: 2023.0" (float value)

D Raises a ValueError because year is not converted

💡 Hint

The int converter converts the URL part to an integer type.

The <int:year> converter converts the URL segment to an integer before passing it to the view. So, year is an integer 2023, and the response is Year: 2023.

📝 Syntax

intermediate

Which URL pattern correctly uses the slug converter?

Select the URL pattern that correctly captures a slug parameter named post_slug.

A path('post/<slug_post>/', views.post_detail)

B path('post/<slug:post_slug>/', views.post_detail)

C path('post/<str:post_slug>/', views.post_detail)

D path('post/<slug>/', views.post_detail)

💡 Hint

The syntax is <converter:name>.

The correct syntax for a slug converter is <slug:post_slug>. Option B uses str converter which is valid but not slug. Option B and D have incorrect parameter names or missing converter.

🔧 Debug

advanced

Why does this URL pattern cause a 404 error for /user/abc123/?

Consider this URL pattern:

path('user//', views.user_profile)

Why does accessing /user/abc123/ return a 404 error?

A Because the user_id parameter is not passed as a string

B Because the view function is missing a required argument

C Because the URL pattern is missing a trailing slash

D Because 'abc123' is not a valid integer, so the pattern does not match

💡 Hint

The int converter only matches digits.

The <int:user_id> converter only matches digits. The string 'abc123' contains letters, so the URL pattern does not match and Django returns 404.

❓ state_output

advanced

What is the type and value of pk in this view?

Given this URL pattern and view:

path('item//', views.item_detail)

def item_detail(request, pk):
    return HttpResponse(type(pk).__name__ + ' ' + str(pk))

What will be the response content when accessing /item/123e4567-e89b-12d3-a456-426614174000/?

A "int 123e4567"

B "str 123e4567-e89b-12d3-a456-426614174000"

C "UUID 123e4567-e89b-12d3-a456-426614174000"

D Raises a ValueError because UUID is not converted

💡 Hint

The uuid converter converts the string to a UUID object.

The <uuid:pk> converter converts the URL string to a UUID object. So, pk is a UUID instance, and type(pk).__name__ is 'UUID'.

🧠 Conceptual

expert

Which statement about Django URL converters is true?

Select the correct statement about Django's built-in URL parameter type converters.

A The <code>slug</code> converter matches only letters, numbers, underscores, and hyphens

B The <code>path</code> converter matches any non-empty string including slashes

C The <code>int</code> converter matches any integer including negative numbers

D The <code>uuid</code> converter matches only lowercase hexadecimal digits without hyphens

💡 Hint

Think about what characters a slug can contain.

The slug converter matches ASCII letters, numbers, underscores, and hyphens. The path converter matches any non-empty string including slashes. The int converter matches only positive integers (digits). The uuid converter matches UUID strings with hyphens and both uppercase and lowercase hex digits.

Practice

1. What does the int converter do in a Django URL pattern?

easy

A. It matches any string including letters and symbols.

B. It matches only integer values and converts them to Python int type.

C. It matches UUID strings only.

D. It matches file paths including slashes.

Solution

1. Step 1: Understand the role of converters

   Converters tell Django what type of data to expect and convert URL parts accordingly.

2. Step 2: Identify the behavior of int converter

   The int converter matches only digits and converts them to Python integers.

3. Final Answer:

   It matches only integer values and converts them to Python int type. -> Option B

4. Quick Check:

   int converter = matches integers [OK]

Hint: int converter matches digits only, converts to int [OK]

Common Mistakes:

• Thinking int matches strings with letters
• Confusing int with slug or str converters
• Assuming int matches UUIDs

2. Which of the following is the correct syntax to capture a slug parameter named post_slug in a Django URL pattern?

easy

A. path('post//', views.post_detail)

B. path('post//', views.post_detail)

C. path('post//', views.post_detail)

D. path('post//', views.post_detail)

Solution

1. Step 1: Identify the correct converter for slugs

   The slug converter matches letters, numbers, underscores, and hyphens.

2. Step 2: Match syntax with converter and parameter name

   The syntax is <slug:post_slug> inside the path string.

3. Final Answer:

   path('post/<slug:post_slug>/', views.post_detail) -> Option A

4. Quick Check:

   slug converter syntax = <slug:name> [OK]

Hint: Use for slug parameters in URL patterns [OK]

Common Mistakes:

• Using int converter for slug parameters
• Mixing UUID or path converters incorrectly
• Missing colon between converter and parameter name

3. Given the URL pattern path('user//', views.profile) and the URL /user/42/, what will be the type and value of user_id in the view?

medium

A. A string '42'

B. A path string including slashes

C. A UUID object

D. An integer 42

Solution

1. Step 1: Analyze the URL pattern converter

   The int converter converts the URL part to an integer.

2. Step 2: Check the URL segment matched

   The URL segment '42' matches the int converter and becomes integer 42.

3. Final Answer:

   An integer 42 -> Option D

4. Quick Check:

   int converter converts to int type [OK]

Hint: int converter converts URL part to integer type [OK]

Common Mistakes:

• Assuming user_id is a string
• Confusing int with uuid or path converters
• Thinking the value includes slashes

4. What is wrong with this URL pattern? path('article//', views.detail) when the URL /article/abc/ is requested.

medium

A. No error, the view receives id='abc' as a string.

B. The pattern should use to accept 'abc'.

C. URL does not match because 'abc' is not an integer, causing a 404 error.

D. The view will raise a ValueError automatically.

Solution

1. Step 1: Understand the int converter behavior

   The int converter only matches digits; 'abc' is not digits.

2. Step 2: Check URL matching result

   Since 'abc' does not match int, Django returns a 404 error (no match).

3. Final Answer:

   URL does not match because 'abc' is not an integer, causing a 404 error. -> Option C

4. Quick Check:

   int converter rejects non-digit URL parts [OK]

Hint: int converter rejects non-digit URL parts, causing 404 [OK]

Common Mistakes:

• Thinking view gets string 'abc' anyway
• Expecting automatic type conversion errors in view
• Confusing 404 with server error

5. You want to capture a URL parameter that can include slashes, such as a file path, in Django. Which converter should you use and why?

hard

A. Use path converter because it matches any string including slashes.

B. Use str converter because it matches strings without slashes.

C. Use slug converter because it matches letters and hyphens.

D. Use uuid converter because it matches unique identifiers.

Solution

1. Step 1: Identify the need to match slashes in URL parameter

   Regular str converter stops at slashes, so it cannot capture paths with slashes.

2. Step 2: Choose the converter that allows slashes

   The path converter matches any string including slashes, perfect for file paths.

3. Final Answer:

   Use path converter because it matches any string including slashes. -> Option A

4. Quick Check:

   path converter = matches strings with slashes [OK]

Hint: Use path converter to capture URL parts with slashes [OK]

Common Mistakes:

• Using str converter which stops at slashes
• Confusing slug or uuid converters for paths
• Expecting int converter to match strings