How to Build a Simple REST API with Flask

Flask is a popular micro web framework for Python that makes it easy to build web applications quickly. In this tutorial, you will learn how to create a simple REST API using Flask.

Prerequisites

• Basic knowledge of Python programming.
• Flask installed on your system (or the ability to install it).

1. Setting Up Your Environment

It is a good practice to create a virtual environment for your project. Navigate to your desired project folder in the terminal and run:

python3 -m venv venv
source venv/bin/activate

This creates a virtual environment and activates it. Once activated, you can install Flask.

2. Installing Flask

Install Flask using pip:

pip install Flask

3. Creating a Simple Flask Application

Create a new file named app.py:

touch app.py

Open app.py in your favorite text editor and add the following code:

from flask import Flask, jsonify, request

app = Flask(__name__)

# Sample data
items = [
    {'id': 1, 'name': 'Item One'},
    {'id': 2, 'name': 'Item Two'}
]

@app.route('/items', methods=['GET'])
def get_items():
    return jsonify(items)

@app.route('/items', methods=['POST'])
def add_item():
    new_item = request.get_json()
    items.append(new_item)
    return jsonify(new_item), 201

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

4. Running the Flask Application

To run your Flask application, execute the following command in the terminal:

python app.py

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

5. Testing Your API

To test your API endpoints, you can use tools like curl or Postman.

Testing the GET Request:

curl http://127.0.0.1:5000/items

This should return a JSON array of items.

Testing the POST Request:

curl -X POST -H "Content-Type: application/json" -d '{"id": 3, "name": "Item Three"}' http://127.0.0.1:5000/items

This command sends a new item to the API. You should receive the new item in the response.

6. Conclusion

Congratulations! You have created a simple REST API using Flask. This API allows you to retrieve and add items dynamically. Flask provides a robust framework for building APIs and web applications, and you can continue to enhance your application by adding features like error handling, authentication, and more.

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Dorian Kane

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