52. Creating a REST API with Flask

1. Basic Flask REST API Setup

A basic Flask setup with a simple route.

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from flask import Flask, jsonify

app = Flask(__name__)

@app.route('/api', methods=['GET'])
def api_home():
    return jsonify({"message": "Welcome to the API!"})

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

This simple API responds with a JSON message at the /api route.

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2. Handling GET Requests

Returning data in JSON format from a GET request.

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from flask import Flask, jsonify

app = Flask(__name__)

data = {
    "user": "Alice",
    "age": 25
}

@app.route('/api/user', methods=['GET'])
def get_user():
    return jsonify(data)

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

The API returns the data dictionary as JSON when accessed via the /api/user route.

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3. Handling POST Requests

Accepting JSON data and responding accordingly.

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from flask import Flask, request, jsonify

app = Flask(__name__)

@app.route('/api/user', methods=['POST'])
def create_user():
    user_data = request.get_json()  # Get JSON data from request
    return jsonify({"message": "User created!", "data": user_data}), 201

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

This snippet allows clients to send JSON data via a POST request and get a response with the data.

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4. Handling PUT Requests

Updating resources via PUT requests.

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from flask import Flask, request, jsonify

app = Flask(__name__)

data = {
    "user": "Alice",
    "age": 25
}

@app.route('/api/user', methods=['PUT'])
def update_user():
    new_data = request.get_json()
    data.update(new_data)  # Update data with new values
    return jsonify({"message": "User updated!", "data": data})

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

This API allows updating an existing user’s data via a PUT request.

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5. Handling DELETE Requests

Deleting a resource via a DELETE request.

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from flask import Flask, jsonify

app = Flask(__name__)

data = {
    "user": "Alice",
    "age": 25
}

@app.route('/api/user', methods=['DELETE'])
def delete_user():
    data.clear()  # Clear the user data
    return jsonify({"message": "User deleted!"})

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

The /api/user route handles a DELETE request to remove the user data.

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6. Query Parameters in GET Requests

Using query parameters to filter results.

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from flask import Flask, request, jsonify

app = Flask(__name__)

@app.route('/api/greet', methods=['GET'])
def greet_user():
    name = request.args.get('name', 'Guest')  # Get 'name' from query params
    return jsonify({"message": f"Hello, {name}!"})

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

This example accepts a query parameter name to customize the greeting message.

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7. Handling URL Parameters

Extracting parameters from the URL.

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from flask import Flask, jsonify

app = Flask(__name__)

@app.route('/api/user/<string:name>', methods=['GET'])
def get_user_by_name(name):
    return jsonify({"message": f"Hello, {name}!"})

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

Here, the name parameter is extracted directly from the URL and used in the response.

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8. Returning Status Codes

Returning appropriate HTTP status codes in responses.

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from flask import Flask, jsonify

app = Flask(__name__)

@app.route('/api/not_found', methods=['GET'])
def not_found():
    return jsonify({"error": "Resource not found"}), 404

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

This snippet demonstrates how to return a 404 status code with a message.

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9. Flask API with Authentication (Basic Auth)

Securing API routes with basic authentication.

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from flask import Flask, jsonify, request
from functools import wraps
import base64

app = Flask(__name__)

# Basic Authentication
def check_auth(username, password):
    return username == 'admin' and password == 'password'

def requires_auth(f):
    @wraps(f)
    def decorated(*args, **kwargs):
        auth = request.headers.get('Authorization')
        if not auth:
            return jsonify({"message": "Authorization required!"}), 403
        auth_type, auth_string = auth.split(' ')
        if auth_type.lower() != 'basic':
            return jsonify({"message": "Invalid auth type!"}), 403
        username, password = base64.b64decode(auth_string).decode('utf-8').split(':')
        if not check_auth(username, password):
            return jsonify({"message": "Invalid credentials!"}), 403
        return f(*args, **kwargs)
    return decorated

@app.route('/api/secure', methods=['GET'])
@requires_auth
def secure_api():
    return jsonify({"message": "You have access!"})

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

This route requires basic authentication using the Authorization header.

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10. Flask API with JSON Schema Validation

Validating JSON data with a schema using marshmallow.

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from flask import Flask, request, jsonify
from marshmallow import Schema, fields, ValidationError

app = Flask(__name__)

class UserSchema(Schema):
    name = fields.String(required=True)
    age = fields.Integer(required=True)

@app.route('/api/user', methods=['POST'])
def create_user():
    try:
        user_data = request.get_json()
        user = UserSchema().load(user_data)  # Validate input data
        return jsonify({"message": "User created!", "data": user}), 201
    except ValidationError as err:
        return jsonify({"error": err.messages}), 400

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

This example shows how to validate input data against a schema using marshmallow.

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These snippets cover a range of common functionalities when building RESTful APIs with Flask, such as handling different HTTP methods, query parameters, authentication, error handling, and validation.