Pagination (PageNumber, Cursor, Limit/Offset) in Django - Step-by-Step Execution

Concept Flow - Pagination (PageNumber, Cursor, Limit/Offset)

Start Request

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Extract Pagination Params

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Limit/Offset

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Calculate Slice

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PageNumber

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Calculate Page Range

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Cursor

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Use Cursor to Fetch

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Query Database with Params

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Return Paginated Results

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End

The server receives pagination parameters (PageNumber, Cursor, or Limit/Offset), calculates which data slice to fetch, queries the database, and returns the paginated results.

Execution Sample

Django

from django.core.paginator import Paginator

items = list(range(1, 21))
paginator = Paginator(items, 5)
page = paginator.page(2)
print(page.object_list)

This code paginates a list of 20 items into pages of 5 items each and prints the items on page 2.

Execution Table

Step	Action	Input/State	Result/Output
1	Create list of items	items = [1..20]	List with 20 numbers created
2	Create Paginator	Paginator(items, 5)	Paginator with 4 pages (5 items each)
3	Request page 2	page = paginator.page(2)	Page object for page 2 created
4	Get items on page 2	page.object_list	[6, 7, 8, 9, 10]
5	Print items	print(page.object_list)	Outputs: [6, 7, 8, 9, 10]
6	End	No more steps	Pagination complete

💡 Reached requested page 2, output items sliced accordingly

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
items	undefined	[1,2,...,20]	[1,2,...,20]	[1,2,...,20]	[1,2,...,20]	[1,2,...,20]
paginator	undefined	undefined	Paginator object (4 pages)	Paginator object (4 pages)	Paginator object (4 pages)	Paginator object (4 pages)
page	undefined	undefined	undefined	Page 2 object	Page 2 object	Page 2 object
page.object_list	undefined	undefined	undefined	undefined	[6,7,8,9,10]	[6,7,8,9,10]

Key Moments - 3 Insights

Why does page 2 return items starting from 6, not 5?

Because pagination pages start counting items from 1, page 1 has items 1-5, so page 2 starts at item 6 as shown in execution_table row 4.

What happens if I request a page number beyond the last page?

Django's Paginator raises an exception if the page number is too high. This is not shown here but you must handle it to avoid errors.

How does Limit/Offset differ from PageNumber pagination?

Limit/Offset uses a start position and count to slice data directly, while PageNumber uses page count and size to calculate slices, as seen in the concept_flow.

Visual Quiz - 3 Questions

Look at the execution_table, what is the output of page.object_list at step 4?

A [1, 2, 3, 4, 5]

B [6, 7, 8, 9, 10]

C [11, 12, 13, 14, 15]

D [16, 17, 18, 19, 20]

💡 Hint

Check the 'Result/Output' column at step 4 in the execution_table

At which step does the paginator know how many pages exist?

A Step 2

B Step 1

C Step 3

D Step 4

💡 Hint

Look at the 'Action' and 'Result/Output' columns in execution_table step 2

If the page size changes from 5 to 10, how does page 2's object_list change?

A It will contain items [1, 2, ..., 10]

B It will contain items [6, 7, 8, 9, 10]

C It will contain items [11, 12, ..., 20]

D It will be empty

💡 Hint

Refer to variable_tracker and how page size affects slicing in the concept_flow

Concept Snapshot

Django Pagination:
- Use Paginator(items, per_page) to split data
- Access pages with paginator.page(number)
- page.object_list gives items on that page
- PageNumber pagination uses page count
- Limit/Offset slices by start and count
- Cursor pagination uses a pointer for next data slice

Full Transcript

This visual execution shows how Django pagination works using PageNumber style. First, a list of 20 items is created. Then, a Paginator object is made with 5 items per page, resulting in 4 pages. Requesting page 2 returns items 6 to 10. The execution table traces each step from list creation to printing the page items. Variables like items, paginator, page, and page.object_list are tracked through the steps. Key moments clarify why page 2 starts at item 6 and differences between pagination types. The quiz tests understanding of output at steps, paginator state, and effects of changing page size.