Python Falcon - Resource Class

Last Updated : 18 Dec, 2023

Python Falcon is a simple web framework that helps developers efficiently manage RESTful APIs. One of its main strengths is how it organizes code using Resource Classes. These classes play a crucial role in Falcon applications, making it easier to handle endpoint logic and improving the clarity and maintainability of the code. As developers explore Falcon, using Resource Classes becomes important. They provide a structured way to create APIs that are both scalable and high-performing.

Python Falcon - Resource Class

In the Falcon world, a Resource class serves as a Python entity that defines how a particular API endpoint behaves. It acts as a guide for handling incoming HTTP requests, going through them, managing the details, and creating the appropriate response. These classes wrap up the complex handling of different HTTP methods (GET, POST, PUT, DELETE, etc.) associated with a specific resource. These classes make sure everything runs smoothly when someone interacts with that part of the system

Features of Python Falcon - Resource Class

Routing Mechanism: Falcon utilizes Resource classes to establish connections between HTTP methods and their corresponding resource endpoints. This is achieved by automatically directing incoming requests to the appropriate Resource class, determined by evaluating the requested URI and HTTP method.
Method Definitions: In Falcon, Resource classes conventionally define methods corresponding to various HTTP methods, such as on_get, on_post, on_put, and more. These methods are responsible for processing incoming requests and generating appropriate responses.
Request and Response Handling: Falcon provides Request and Response objects as inputs to the methods within the Resource class. These objects encapsulate the details of the incoming request and the intended response, facilitating streamlined handling of data within the framework.
Statelessness Principle: Falcon follows a stateless approach, advocating the development of APIs that operate independently for each request. Resource classes are expected to align with this principle, ensuring that each request is managed autonomously without relying on shared states between different requests. This design philosophy enhances scalability and simplifies the maintenance of Falcon-based applications.

Create Python Falcon - Resource Class

Let's navigate through the journey of shaping a straightforward Falcon Resource class

Step 1: Basic Falcon Class

In this example, we've created a basic Falcon Resource class named HelloWorldResource with an on_get method. This method will be invoked when a GET request is made to the corresponding endpoint.

Python3

import falcon
class HelloWorldResource:
    def on_get(self, req, resp):
        resp.status = falcon.HTTP_200
        resp.body = "Hello, World!"

Step 2: Routing Requests to Resource Classes

Routing requests to Resource classes is a fundamental aspect of Falcon. This is achieved through the add_route method of the Falcon API instance. Here's an example:

Here, we've created a Falcon app instance and added a route that maps the '/hello' URI to our HelloWorldResource class. Now, when a GET request is made to '/hello', the on_get method of HelloWorldResource will be executed.

Python3

import falcon
app = falcon.App()
hello_world_resource = HelloWorldResource()
app.add_route('/hello', hello_world_resource)

CRUD Operation in Python Falcon - Resource Class

Here ,the code defines a Falcon API with a resource class named `TaskResource` to manage tasks. The resource supports GET, POST, PUT, and DELETE methods. The `on_get` method retrieves the list of tasks, the `on_post` method adds a new task, the `on_put` method updates a task, and the `on_delete` method deletes a task based on the specified criteria. Additionally, the code includes an HTML UI for interacting with the task management system. The UI allows users to add, update, and delete tasks through a web interface. The Falcon app is configured to serve this HTML UI through a separate `HTMLResource` class, and the entire application is run on a local server at http://127.0.0.1:8000. Users can access the web interface to manage tasks through the provided HTML UI.

Python3

import falcon
import json

class TaskResource:
    def __init__(self):
        self.tasks = []
        self.next_id = 1
# Get Method in Falcon
    def on_get(self, req, resp):
        resp.status = falcon.HTTP_200
        resp.media = {"tasks": self.tasks}
# Post Method in Falcon
    def on_post(self, req, resp):
        data = json.loads(req.bounded_stream.read().decode("utf-8"))

        if "title" not in data:
            resp.status = falcon.HTTP_400
            resp.media = {"error": "Title is required"}
            return

        new_task = {"id": self.next_id, "title": data["title"]}
        self.tasks.append(new_task)
        self.next_id += 1

        resp.status = falcon.HTTP_201
        resp.media = new_task

# Put Method in Falcon
    def on_put(self, req, resp):
        data = json.loads(req.bounded_stream.read().decode("utf-8"))

        if "current_title" not in data or "new_title" not in data:
            resp.status = falcon.HTTP_400
            resp.media = {"error": "Both current_title and new_title are required"}
            return

        for task in self.tasks:
            if task["title"] == data["current_title"]:
                task["title"] = data["new_title"]
                resp.status = falcon.HTTP_200
                resp.media = task
                return

        resp.status = falcon.HTTP_404
        resp.media = {"error": "Task not found"}
        
# Delete Method in Falcon
    def on_delete(self, req, resp):
        data = json.loads(req.bounded_stream.read().decode("utf-8"))

        if "title" not in data:
            resp.status = falcon.HTTP_400
            resp.media = {"error": "Title is required"}
            return

        for task in self.tasks:
            if task["title"] == data["title"]:
                self.tasks.remove(task)
                resp.status = falcon.HTTP_200
                resp.media = {"message": "Task deleted"}
                return

        resp.status = falcon.HTTP_404
        resp.media = {"error": "Task not found"}


# Create a Falcon app
app = falcon.App()

# Create an instance of TaskResource
task_resource = TaskResource()

# Add routes to the app
app.add_route("/tasks", task_resource)

# HTML UI (cleaned up)
html_ui = """
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Task Manager</title>
    <style>
        body {
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
            background-color: #f9f9f9;
            margin: 0;
            padding: 0;
        }

        header {
            background-color: #333; 
            color: #fff;
            text-align: center;
            padding: 1rem;
        }

        main {
            max-width: 800px;
            margin: 20px auto;
            background-color: #fff;
            padding: 20px;
            border-radius: 8px;
            box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
        }

        form {
            display: flex;
            gap: 10px;
            margin-bottom: 20px;
        }

        label {
            font-weight: bold;
            color: #333;
        }

        input {
            padding: 8px;
            border: 1px solid #ccc;
            border-radius: 3px;
            width: 70%;
            font-size: 14px;
        }

        button {
            padding: 8px 15px;
            background-color: #007bff;
            color: #fff;
            border: none;
            border-radius: 3px;
            cursor: pointer;
            font-size: 14px;
        }

        button:hover {
            background-color: #0056b3;
        }

        h1 {
            color: white;
            font-size: 1.5rem;
            margin-bottom: 10px;
        }

        h2 {
            color: #28a745;
            font-size: 3rem;
        }

        ul {
            list-style-type: none;
            padding: 0;
        }

        li {
            margin: 10px 0;
            padding: 10px;
            border: 1px solid #ccc;
            border-radius: 5px;
            display: flex;
            justify-content: space-between;
            align-items: center;
        }

        li:hover {
            background-color: #f0f0f0;
        }

        button.update,
        button.delete {
            padding: 5px 10px;
            font-size: 0.9rem;
        }

        button.update {
            background-color: green;
            color: #fff;
            border: none;
            margin-right: 5px;
        }

        button.delete {
            background-color: red;
            color: #fff;
            border: none;
        }
    </style>
</head>
<body>
    <header>
        <h2>GeeksforGeeks</h2>
        <h1>Task Manager</h1>
    </header>
    
    <main>
        <form id="taskForm">
            <label for="taskTitle">Task Title:</label>
            <input type="text" id="taskTitle" required>
            <button type="submit">Add Task</button>
        </form>

        <h3>Task List</h3>
        <ul id="taskList"></ul>
    </main>

    <script>
    function fetchTasks() {
        fetch('/tasks')
            .then(response => response.json())
            .then(data => {
                const taskList = document.getElementById('taskList');
                taskList.innerHTML = '';

                data.tasks.forEach(task => {
                    const listItem = document.createElement('li');
                    listItem.textContent = task.title;

                    const updateButton = document.createElement('button');
                    updateButton.textContent = 'Update';
                    updateButton.onclick = () => handleUpdate(task.title);
                    listItem.appendChild(updateButton);

                    const deleteButton = document.createElement('button');
                    deleteButton.textContent = 'Delete';
                    deleteButton.onclick = () => handleDelete(task.title);
                    listItem.appendChild(deleteButton);

                    taskList.appendChild(listItem);
                });
            });
    }

    function handleFormSubmission(event) {
        event.preventDefault();

        const taskTitle = document.getElementById('taskTitle').value;

        fetch('/tasks', {
            method: 'POST',
            headers: {
                'Content-Type': 'application/json',
            },
            body: JSON.stringify({ title: taskTitle }),
        })
        .then(response => response.json())
        .then(data => {
            console.log('Task added:', data);
            fetchTasks();
        });

        document.getElementById('taskTitle').value = '';
    }

    function handleUpdate(currentTitle) {
        const newTitle = prompt('Enter new title:');
        if (newTitle !== null) {
            fetch('/tasks', {
                method: 'PUT',
                headers: {
                    'Content-Type': 'application/json',
                },
                body: JSON.stringify({ current_title: currentTitle, new_title: newTitle }),
            })
            .then(response => response.json())
            .then(data => {
                console.log('Task updated:', data);
                fetchTasks();
            });
        }
    }

    function handleDelete(title) {
        const confirmDelete = confirm(`Are you sure you want to delete the task "${title}"?`);
        if (confirmDelete) {
            fetch('/tasks', {
                method: 'DELETE',
                headers: {
                    'Content-Type': 'application/json',
                },
                body: JSON.stringify({ title: title }),
            })
            .then(response => response.json())
            .then(data => {
                console.log('Task deleted:', data);
                fetchTasks();
            });
        }
    }
    document.getElementById('taskForm').addEventListener('submit', handleFormSubmission);
    fetchTasks();
</script>
</body>
</html>
"""
# Falcon route to serve the HTML UI
class HTMLResource:
    def on_get(self, req, resp):
        resp.content_type = "text/html"
        resp.text = html_ui

app.add_route("/", HTMLResource())

# Run the app
if __name__ == "__main__":
    from wsgiref import simple_server

    httpd = simple_server.make_server("127.0.0.1", 8000, app)
    print("Serving on http://127.0.0.1:8000")
    httpd.serve_forever()

Run the Server

python script_name.py

Output

Conclusion

The Falcon Resource class is a powerful tool for building RESTful APIs with Python. By encapsulating endpoint-specific logic in Resource classes, Falcon promotes clean, modular, and maintainable API code. Understanding how to create and use Resource classes is essential for anyone developing APIs with Falcon, and it forms the backbone of efficient and scalable API applications. As you explore Falcon further, you'll discover additional features and capabilities that make it a versatile and lightweight framework for API development in Python.