Welcome to the final lesson of our course on enhancing your To-Do API. Today, we will focus on implementing pagination. You have already learned how to filter and sort your To-Do items, which are essential for making your API more user-friendly and efficient. Imagine your app grows and some users have thousands of tasks. Loading all of them to the web-page can be inefficient.

Pagination allows you to break down large data sets into smaller, manageable chunks. This not only improves performance but also enhances the user experience by preventing information overload.

By the end of this lesson, you'll be able to implement and customize pagination for your To-Do API using Django Rest Framework’s PageNumberPagination. Let's get started!

To enhance our To-Do API with pagination, we'll use Django Rest Framework’s PageNumberPagination. This allows us to manage large datasets by serving data in smaller, more manageable pages.

First, create a pagination.py file in your app directory. Here’s a simple custom pagination class:

Python
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1# pagination.py
2from rest_framework.pagination import PageNumberPagination
3
4class TodoPagination(PageNumberPagination):
5    page_size = 2
6    page_size_query_param = 'page_size'
7    max_page_size = 10

Pagination is the process of dividing a large set of data into sequential pages. In Django Rest Framework, the PageNumberPagination class is a built-in utility to handle this. Here's how it works:

• page_size: This attribute sets the default number of records to be displayed per page. In our case, it is set to 2.
• page_size_query_param: This attribute allows the client to define the number of records per page by passing a query parameter (e.g., ?page_size=5).
• max_page_size: This attribute sets an upper limit on the number of records per page that the client can request. This is useful for preventing misuse where a client might request an excessively large page size.

By using these settings, you can efficiently manage the dataset and provide a better user experience.

Next, we need to apply this pagination class to our views. Update the views.py file as follows:

Python
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1# views.py
2from rest_framework.filters import OrderingFilter
3from .pagination import TodoPagination  # Importing the custom pagination class
4
5class TodoListCreate(generics.ListCreateAPIView):
6    queryset = Todo.objects.all()
7    serializer_class = TodoSerializer
8    filter_backends = [OrderingFilter]
9    ordering_fields = ['priority', 'task']
10    pagination_class = TodoPagination  # Setting custom pagination class
11
12# Keep other views unchanged
13class TodoDetail(generics.RetrieveAPIView):
14    queryset = Todo.objects.all()
15    serializer_class = TodoSerializer
16
17class TodoUpdate(generics.UpdateAPIView):
18    queryset = Todo.objects.all()
19    serializer_class = TodoSerializer
20
21class TodoDelete(generics.DestroyAPIView):
22    queryset = Todo.objects.all()
23    serializer_class = TodoSerializer

We import the custom TodoPagination class and set it in the TodoListCreate view using the pagination_class attribute. Now, our To-Do API is capable of paginating the results, making it easier to handle large datasets.

Pagination is essential for handling large datasets in many real-world applications. Here are some common use cases:

1. E-commerce Sites: Displaying a large catalog of products without overwhelming the user.
2. Social Media Platforms: Loading posts, comments, and user activities in a manageable way.
3. Content Management Systems: Managing articles, blog posts, and media files efficiently.
4. Project Management Tools: Organizing and displaying numerous tasks and projects systematically.
5. Financial Services: Viewing transaction histories, account activities, and logs.

Pagination makes these applications more responsive and manageable by breaking down data into smaller segments.

To see pagination in action, let's make some HTTP requests. Here is a send_request.py script that demonstrates how to interact with the paginated API:

Python
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1import requests
2import json
3
4base_url = 'http://0.0.0.0:3000/api/todos/'
5
6# Function to print response items
7def print_response_items(response):
8    for item in response.json():
9        print(json.dumps(item, indent=2))
10
11# Create TODO items
12todos = [
13    {"task": "Buy groceries", "completed": False, "priority": 1},
14    {"task": "Prepare presentation", "completed": True, "priority": 2},
15    {"task": "Go to gym", "completed": False, "priority": 3},
16    {"task": "Finish homework", "completed": True, "priority": 1},
17    {"task": "Organize books", "completed": False, "priority": 2},
18    {"task": "Clean the house", "completed": True, "priority": 3},
19]
20
21# Create TODO items
22for todo in todos:
23    response = requests.post(base_url, json=todo)
24    print(f'Created TODO: {response.json()}')
25
26# Pagination examples
27
28# Get first page of TODOs
29response = requests.get(base_url, params={'page': 1})
30print('TODOs page 1:')
31print_response_items(response)
32
33# Get second page of TODOs
34response = requests.get(base_url, params={'page': 2})
35print('TODOs page 2:')
36print_response_items(response)

• The script first creates several TODO items.
• It then fetches the first and second pages of TODOs with the default page size.
• The print_response_items function helps visualize the responses.

Let's extend our script to test pagination with a custom page size:

Python
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1import requests
2import json
3
4base_url = 'http://0.0.0.0:3000/api/todos/'
5
6# Function to print response items
7def print_response_items(response):
8    for item in response.json():
9        print(json.dumps(item, indent=2))
10
11# Pagination examples with custom page size
12
13# Get first page with a custom page size of 3
14response = requests.get(base_url, params={'page': 1, 'page_size': 3})
15print('TODOs page 1 with page size 3:')
16print_response_items(response)
17
18# Get second page with a custom page size of 3
19response = requests.get(base_url, params={'page': 2, 'page_size': 3})
20print('TODOs page 2 with page size 3:')
21print_response_items(response)

• The script fetches the first and second pages of TODOs with a custom page size of 3.
• This demonstrates how pagination can be customized based on user preferences.

As these examples show, pagination effectively splits large datasets into manageable pages, greatly enhancing the user experience.

In real-world applications, you might need to gather all items by iterating through each page of a paginated API. Here’s how you can achieve that using a loop in your send_request.py script:

Python
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1import requests
2import json
3
4base_url = 'http://0.0.0.0:3000/api/todos/'
5
6# Function to print response items
7def print_response_items(response):
8    for item in response.json()['results']:
9        print(json.dumps(item, indent=2))
10
11# Function to get all TODO items
12def get_all_todos():
13    page = 1
14    while True:
15        response = requests.get(base_url, params={'page': page})
16        if response.status_code != 200 or not response.json()['results']:
17            break
18        print(f'TODOs page {page}:')
19        print_response_items(response)
20        page += 1
21
22# Fetch and print all TODO items
23get_all_todos()

• The function get_all_todos uses a loop to iterate through all pages by incrementing the page parameter until there are no more results.
• The response JSON structure is assumed to have a 'results' key that holds the paginated items, based on typical Django Rest Framework responses.
• The loop stops when a response returns a status code other than 200 or there are no more results.

In this lesson, we covered how to enhance your To-Do API by implementing pagination. We set up Django Rest Framework’s PageNumberPagination, customized pagination settings, and tested the pagination functionality using HTTP requests.

Key takeaways include:

• Pagination improves performance and user experience.
• Customizing pagination settings to fit specific needs.
• Testing your API to ensure it works as expected.

Congratulations on reaching the end of this course! You have learned essential skills to enhance and optimize your To-Do API by implementing filtering, sorting, and pagination. These capabilities will not only make your API more efficient but also significantly improve the user experience.

As you move forward, I encourage you to apply these concepts to your own projects and continue exploring more advanced topics in API development. Great work, and keep coding!