Page-based pagination in Rest API

Introduction

Page-based pagination helps split large lists of data into smaller, easy-to-handle pages. This makes loading and viewing data faster and simpler.

When showing search results on a website with many items.

When displaying user comments or posts in chunks instead of all at once.

When loading product lists in an online store page by page.

When an API returns a large dataset and you want to limit how much data is sent at once.

When you want users to navigate through data step-by-step without overwhelming them.

Syntax

Rest API

GET /items?page=2&limit=10

page is the page number you want to see.

limit is how many items to show per page.

Examples

Get the first page of products, showing 20 items.

Rest API

GET /products?page=1&limit=20

Get the third page of comments, 5 comments per page.

Rest API

GET /comments?page=3&limit=5

Get the tenth page of users, 50 users per page.

Rest API

GET /users?page=10&limit=50

Sample Program

This small web app uses Flask to create an API endpoint /items. It accepts page and limit as query parameters. It returns a JSON with the requested page of items from a list of 100 numbers.

Rest API

from flask import Flask, request, jsonify

app = Flask(__name__)

# Sample data: list of 100 numbers
items = list(range(1, 101))

@app.route('/items')
def get_items():
    # Get page and limit from query parameters, default to page=1, limit=10
    page = int(request.args.get('page', 1))
    limit = int(request.args.get('limit', 10))

    # Calculate start and end indexes
    start = (page - 1) * limit
    end = start + limit

    # Slice the items list to get current page items
    page_items = items[start:end]

    # Prepare response with page info
    response = {
        'page': page,
        'limit': limit,
        'total_items': len(items),
        'items': page_items
    }
    return jsonify(response)

if __name__ == '__main__':
    app.run(debug=True)

Important Notes

Page numbers usually start at 1, not 0.

If the requested page is beyond the available data, return an empty list.

Always validate and sanitize query parameters to avoid errors.

Summary

Page-based pagination splits data into pages using page number and limit.

It improves performance and user experience by loading data in chunks.

Use query parameters like page and limit to control pagination.

Practice

1. What is the main purpose of page-based pagination in REST APIs?

easy

A. To split large data into smaller pages for easier loading

B. To combine all data into one large response

C. To sort data alphabetically

D. To encrypt data before sending

Solution

1. Step 1: Understand pagination concept

   Pagination divides data into smaller parts called pages to avoid sending everything at once.

2. Step 2: Identify purpose in REST APIs

   Page-based pagination uses page number and limit to load data in chunks, improving performance and user experience.

3. Final Answer:

   To split large data into smaller pages for easier loading -> Option A

4. Quick Check:

   Pagination = split data into pages [OK]

Hint: Pagination means splitting data into pages [OK]

Common Mistakes:

• Thinking pagination sorts data
• Confusing pagination with encryption
• Assuming pagination combines all data

2. Which of the following is the correct way to request page 3 with 10 items per page using query parameters?

easy

A. /items?size=10&page=3

B. /items?limit=3&page=10

C. /items?page=10&limit=3

D. /items?page=3&limit=10

Solution

1. Step 1: Identify standard query parameters

   Page-based pagination commonly uses page for page number and limit for items per page.

2. Step 2: Match parameters to values

   Requesting page 3 with 10 items means page=3 and limit=10.

3. Final Answer:

   /items?page=3&limit=10 -> Option D

4. Quick Check:

   page=3 and limit=10 [OK]

Hint: Use page=number and limit=items per page [OK]

Common Mistakes:

• Swapping page and limit values
• Using wrong parameter names like size
• Mixing up page number with limit count

3. Given the API endpoint /products?page=2&limit=5 and a total of 12 products, how many products will be returned in the response?

medium

A. 2

B. 7

C. 5

D. 12

Solution

1. Step 1: Calculate items per page

   The limit is 5, so each page should have up to 5 products.

2. Step 2: Determine products on page 2

   Page 1 has products 1-5, page 2 has products 6-10, so page 2 returns 5 products.

3. Final Answer:

   5 -> Option C

4. Quick Check:

   limit = 5 products per page [OK]

Hint: Page 2 with limit 5 returns 5 items if available [OK]

Common Mistakes:

• Counting all 12 products instead of page limit
• Assuming leftover products on page 2
• Confusing page number with total items

4. You have this code snippet for pagination parameters:

page = int(request.GET.get('page', 1))
limit = int(request.GET.get('limit', 10))
start = (page - 1) * limit
end = page * limit
items = data[start:end]

What is the error if page is 0?

medium

A. It causes negative start index, returning wrong items

B. It returns the last page instead of first

C. It raises a syntax error

D. It ignores the limit parameter

Solution

1. Step 1: Calculate start index with page=0

   start = (0 - 1) * limit = -1 * limit = negative number.

2. Step 2: Understand slicing with negative start

   Negative start index in slicing returns items from the end, causing wrong data to be returned.

3. Final Answer:

   It causes negative start index, returning wrong items -> Option A

4. Quick Check:

   page=0 causes negative start index [OK]

Hint: Page must be >= 1 to avoid negative start index [OK]

Common Mistakes:

• Assuming page=0 is valid
• Expecting syntax error instead of logic error
• Ignoring negative slicing effects

5. You want to implement page-based pagination for an API returning 23 items with a limit of 7 per page. How many pages will the client need to request to get all items?

hard

A. 3

B. 4

C. 5

D. 7

Solution

1. Step 1: Calculate full pages

   Each page holds 7 items, so 3 full pages hold 21 items (3 * 7 = 21).

2. Step 2: Calculate remaining items

   23 total items - 21 = 2 items remain, needing one more page.

3. Step 3: Total pages needed

   3 full pages + 1 partial page = 4 pages total.

4. Final Answer:

   4 -> Option B

5. Quick Check:

   23 items / 7 per page = 4 pages [OK]

Hint: Divide total items by limit, round up for pages [OK]

Common Mistakes:

• Ignoring leftover items needing extra page
• Rounding down instead of up
• Assuming pages equal limit count