Pagination (PageNumber, Cursor, Limit/Offset) in Django - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this Django PageNumberPagination response?

Given a Django REST Framework view using PageNumberPagination with page_size=3, what will the JSON response contain when requesting page 2?

Django

from rest_framework.pagination import PageNumberPagination
from rest_framework.response import Response

class MyPagination(PageNumberPagination):
    page_size = 3

# Assume queryset has 7 items indexed 1 to 7

# Request: GET /items/?page=2

# What will be the 'results' length in the response?

A The 'results' list will contain 3 items (items 4, 5, 6).

B The 'results' list will contain 1 item (item 7 only).

C The 'results' list will contain 4 items (items 4, 5, 6, 7).

D The 'results' list will be empty because page 2 is invalid.

💡 Hint

PageNumberPagination divides items into pages of fixed size. Page 1 has items 1-3, page 2 has items 4-6, and so on.

With 7 items and page size 3, page 1 has items 1-3, page 2 has items 4-6, and page 3 has item 7. So page 2 returns 3 items.

📝 Syntax

intermediate

Which option correctly sets up CursorPagination in Django REST Framework?

Choose the correct way to define a cursor pagination class with a page size of 5 and ordering by 'created' field.

A

class MyCursorPagination(CursorPagination):
    page_size = 5
    ordering = 'created'

B

class MyCursorPagination(CursorPagination):
    page_size = 5
    ordering = created

C

class MyCursorPagination(CursorPagination):
    page_size = 5
    ordering = ('created')

D

class MyCursorPagination(CursorPagination):
    page_size = 5
    ordering = ['created']

💡 Hint

The ordering attribute expects an iterable of strings.

The ordering attribute must be a list or tuple of strings. Option D uses a list with one string 'created'.

🔧 Debug

advanced

Why does this LimitOffsetPagination code raise a TypeError?

Examine the following Django REST Framework pagination class and identify why it raises a TypeError when used.

Django

from rest_framework.pagination import LimitOffsetPagination

class MyLimitOffsetPagination(LimitOffsetPagination):
    default_limit = '10'

# Using this pagination causes TypeError: unsupported operand type(s) for -: 'str' and 'int'

A The class must define a max_limit attribute to avoid errors.

B LimitOffsetPagination requires overriding the paginate_queryset method.

C default_limit is set as a string instead of an integer.

D The TypeError is caused by missing a call to super().__init__() in the class.

💡 Hint

Check the type of default_limit and how it is used internally.

LimitOffsetPagination expects default_limit as an integer. Setting it as a string causes arithmetic operations to fail.

❓ state_output

advanced

What is the value of 'next' in this PageNumberPagination response?

Given a queryset of 12 items and PageNumberPagination with page_size=5, what will the 'next' URL be when requesting page 2?

Django

# Request: GET /api/items/?page=2
# Page size: 5
# Total items: 12

# What is the 'next' URL in the paginated response?

A "/api/items/?page=3"

B "/api/items/?page=4"

C null

D "/api/items/?page=2"

💡 Hint

Calculate total pages and which page comes after page 2.

With 12 items and page size 5, total pages = 3 (5+5+2). Page 2's next page is page 3, so 'next' URL points to page 3.

🧠 Conceptual

expert

Which pagination method is best for infinite scrolling with stable ordering?

You want to implement infinite scrolling in a Django REST Framework API. The data changes frequently, and you want to avoid skipping or repeating items when users scroll. Which pagination method is best?

A LimitOffsetPagination because it allows skipping items by offset.

B CursorPagination because it uses a cursor to track position and handles data changes well.

C PageNumberPagination because it is simple and uses page numbers.

D No pagination; load all items at once for smooth scrolling.

💡 Hint

Consider how data changes affect pagination stability and user experience.

CursorPagination uses a cursor based on item ordering, preventing duplicates or skips even if data changes. It is ideal for infinite scrolling.

Practice

1. Which Django REST Framework pagination style uses a page number to fetch specific pages of data?

easy

A. PageNumberPagination

B. CursorPagination

C. LimitOffsetPagination

D. OffsetPagination

Solution

1. Step 1: Understand pagination styles

   PageNumberPagination uses page numbers like 1, 2, 3 to get data pages.

2. Step 2: Match style to description

   CursorPagination uses a cursor token, LimitOffsetPagination uses limit and offset numbers, so they don't use page numbers.

3. Final Answer:

   PageNumberPagination -> Option A

4. Quick Check:

   Page number style = PageNumberPagination [OK]

Hint: PageNumberPagination uses simple page numbers like 1, 2, 3 [OK]

Common Mistakes:

• Confusing CursorPagination with page numbers
• Thinking LimitOffsetPagination uses page numbers
• Assuming OffsetPagination is a valid DRF style

2. Which of the following is the correct way to set LimitOffsetPagination in Django REST Framework settings?

easy

A. "DEFAULT_PAGINATION_CLASS": "rest_framework.pagination.OffsetPagination"

B. "DEFAULT_PAGINATION_CLASS": "rest_framework.pagination.PageNumberPagination"

C. "DEFAULT_PAGINATION_CLASS": "rest_framework.pagination.LimitOffsetPagination"

D. "DEFAULT_PAGINATION_CLASS": "rest_framework.pagination.CursorPagination"

Solution

1. Step 1: Identify correct class path

   LimitOffsetPagination is located at rest_framework.pagination.LimitOffsetPagination.

2. Step 2: Verify syntax for settings

   The setting key is DEFAULT_PAGINATION_CLASS and the value is the full class path as a string.

3. Final Answer:

   "DEFAULT_PAGINATION_CLASS": "rest_framework.pagination.LimitOffsetPagination" -> Option C

4. Quick Check:

   Correct class path and setting key = "DEFAULT_PAGINATION_CLASS": "rest_framework.pagination.LimitOffsetPagination" [OK]

Hint: Use full class path string for pagination in settings [OK]

Common Mistakes:

• Using OffsetPagination which does not exist
• Missing quotes around class path string
• Mixing pagination class names

3. Given this code snippet using CursorPagination, what will be the value of the next cursor if the current cursor is 'abc123' and page size is 2?

class MyCursorPagination(CursorPagination):
    page_size = 2

paginator = MyCursorPagination()
next_cursor = paginator.get_next_link()

medium

A. A tuple with offset and limit values

B. An integer representing the next page number

C. None, because get_next_link() returns nothing

D. A URL containing a cursor parameter with a new encoded cursor

Solution

1. Step 1: Understand CursorPagination behavior

   CursorPagination returns URLs with encoded cursor tokens for next pages, not page numbers or tuples.

2. Step 2: Analyze get_next_link() output

   get_next_link() returns a URL string containing the next cursor parameter for pagination.

3. Final Answer:

   A URL containing a cursor parameter with a new encoded cursor -> Option D

4. Quick Check:

   CursorPagination next link = URL with cursor [OK]

Hint: CursorPagination returns URLs with cursor tokens, not numbers [OK]

Common Mistakes:

• Expecting page numbers from CursorPagination
• Thinking get_next_link() returns None
• Confusing limit/offset with cursor

4. You have this Django REST Framework view using LimitOffsetPagination but it raises an error:

class MyLimitOffsetPagination(LimitOffsetPagination):
    default_limit = '10'

class MyView(ListAPIView):
    pagination_class = MyLimitOffsetPagination
    queryset = MyModel.objects.all()
    serializer_class = MySerializer

What is the likely cause of the error?

medium

A. pagination_class should be a string path, not a class

B. default_limit should be an integer, not a string

C. ListAPIView does not support pagination

D. queryset must be a list, not a QuerySet

Solution

1. Step 1: Check default_limit type

   default_limit must be an integer, but it is set as a string '10', causing a type error.

2. Step 2: Verify other parts

   pagination_class can be a class, ListAPIView supports pagination, queryset can be a QuerySet.

3. Final Answer:

   default_limit should be an integer, not a string -> Option B

4. Quick Check:

   default_limit type error = default_limit should be an integer, not a string [OK]

Hint: default_limit must be int, not quoted string [OK]

Common Mistakes:

• Setting default_limit as string instead of int
• Thinking pagination_class must be string path
• Assuming ListAPIView disables pagination

5. You want to implement pagination for a large dataset where new items are frequently added. Which pagination style is best to avoid duplicate or missing items when users navigate pages?

hard

A. CursorPagination

B. PageNumberPagination

C. LimitOffsetPagination

D. No pagination

Solution

1. Step 1: Understand pagination challenges with dynamic data

   PageNumber and LimitOffset can cause duplicates or missing items if data changes between requests.

2. Step 2: Identify pagination style that handles dynamic data well

   CursorPagination uses a stable cursor based on item order, preventing duplicates or skips when data changes.

3. Final Answer:

   CursorPagination -> Option A

4. Quick Check:

   Dynamic data needs CursorPagination [OK]

Hint: Use CursorPagination for changing data to avoid duplicates [OK]

Common Mistakes:

• Choosing PageNumberPagination for dynamic data
• Thinking LimitOffsetPagination handles data changes well
• Ignoring pagination for large datasets