Here is a simple yet complete template for a RESTful API using Flask and the Flask-RESTful extension, which is a common and effective way to build APIs.

This example creates a simple “To-Do List” API where you can get, create, update, and delete tasks.

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1. Prerequisites

First, you’ll need to install Flask and Flask-RESTful.

Bash

pip install flask flask-restful

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2. The API Code (app.py)

Create a file named app.py and paste the following code into it. The comments explain what each part does.

Python

# Import necessary libraries
from flask import Flask, request
from flask_restful import Resource, Api, reqparse, abort

# Initialize the Flask application
app = Flask(__name__)
# Initialize the Flask-RESTful API
api = Api(app)

# A simple in-memory database (a dictionary) to store our tasks
TASKS = {
    'task1': {'task': 'build a RESTful API'},
    'task2': {'task': 'learn more about Flask'},
    'task3': {'task': 'profit!'},
}

# --- Helper Functions ---
def abort_if_task_doesnt_exist(task_id):
    """Function to check if a task ID exists in our database."""
    if task_id not in TASKS:
        abort(404, message=f"Task {task_id} doesn't exist")

# --- Argument Parser ---
# This helps validate and parse incoming request data for POST and PUT
parser = reqparse.RequestParser()
parser.add_argument('task', type=str, required=True, help='Task description cannot be blank!')


# --- Resource for a single task ---
# This resource will handle GET, DELETE, and PUT requests for a specific task.
class Task(Resource):
    def get(self, task_id):
        """Retrieve a single task."""
        abort_if_task_doesnt_exist(task_id)
        return TASKS[task_id]

    def delete(self, task_id):
        """Delete a task."""
        abort_if_task_doesnt_exist(task_id)
        del TASKS[task_id]
        # Return an empty response with a 204 No Content status code
        return '', 204

    def put(self, task_id):
        """Update a task."""
        abort_if_task_doesnt_exist(task_id)
        args = parser.parse_args()
        task = {'task': args['task']}
        TASKS[task_id] = task
        return task, 200


# --- Resource for the list of all tasks ---
# This resource will handle GET requests for all tasks and POST to create new tasks.
class TaskList(Resource):
    def get(self):
        """Retrieve the list of all tasks."""
        return TASKS

    def post(self):
        """Create a new task."""
        args = parser.parse_args()
        # Create a new task ID (simple incrementing logic)
        task_id = f'task{int(max(TASKS.keys()).lstrip("task")) + 1}'
        TASKS[task_id] = {'task': args['task']}
        # Return the newly created task with a 201 Created status code
        return TASKS[task_id], 201


# --- API Resource Routing ---
# This is where we define the URLs for our resources.
# The '/tasks' endpoint will be handled by the TaskList resource.
api.add_resource(TaskList, '/tasks')

# The '/tasks/<task_id>' endpoint will be handled by the Task resource.
# The <task_id> part is a variable that will be passed to the methods (get, put, delete).
api.add_resource(Task, '/tasks/<string:task_id>')


# --- Main execution block ---
# This runs the Flask development server.
# debug=True provides helpful error messages and auto-reloads the server on code changes.
if __name__ == '__main__':
    app.run(debug=True)

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3. How to Run the API

1. Open your terminal or command prompt.
2. Navigate to the directory where you saved app.py.
3. Run the application with the following command:Bashpython app.py

You should see output indicating that the server is running, typically on http://127.0.0.1:5000/.

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4. How to Interact with the API

You can use a tool like curl in your terminal, or a GUI application like Postman, to send requests to your new API. Here are the curl commands:

GET all tasks

Bash

curl http://127.0.0.1:5000/tasks

Expected Output:

JSON

{"task1": {"task": "build a RESTful API"}, "task2": {"task": "learn more about Flask"}, "task3": {"task": "profit!"}}

GET a single task

Bash

curl http://127.0.0.1:5000/tasks/task2

Expected Output:

JSON

{"task": "learn more about Flask"}

DELETE a task

curl http://127.0.0.1:5000/tasks/task3 -X DELETE

Bash

(No JSON output, but the command succeeds. You can run the GET all command again to verify it’s gone.)

POST (create) a new task

Bash

curl http://127.0.0.1:5000/tasks -X POST -H "Content-Type: application/json" -d '{"task": "go to the store"}'

Expected Output:

JSON

{"task": "go to the store"}

(This will be created as task4.)

PUT (update) a task

Bash

curl http://127.0.0.1:5000/tasks/task1 -X PUT -H "Content-Type: application/json" -d '{"task": "build an AWESOME RESTful API"}'

Expected Output:

JSON

{"task": "build an AWESOME RESTful API"}

This template provides a solid foundation. You can expand it by connecting it to a real database (like PostgreSQL with SQLAlchemy), adding authentication, and structuring your project into multiple files for better organization.