Flask Blueprint CRUD

Here's a basic example of a CRUD Flask application using a single Blueprint and MySQL. Please note that we'll use Flask-SQLAlchemy for ORM and Flask-Marshmallow for request validation and serialization.

Please, install necessary packages:

Here's the code:

from flask import Flask, request, Blueprint, jsonify
from flask_sqlalchemy import SQLAlchemy
from flask_marshmallow import Marshmallow

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql://username:password@localhost/dbname'
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False

db = SQLAlchemy(app)
ma = Marshmallow(app)

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(80), unique=True)
    usernumber = db.Column(db.String(20), unique=True)
    comment = db.Column(db.String(200))

    def __init__(self, username, usernumber, comment):
        self.username = username
        self.usernumber = usernumber
        self.comment = comment

class UserSchema(ma.SQLAlchemyAutoSchema):
    class Meta:
        model = User
        load_instance = True

user_schema = UserSchema()
users_schema = UserSchema(many=True)

bp = Blueprint('user_api', __name__)

@bp.route('/user', methods=['POST'])
def add_user():
    username = request.json['username']
    usernumber = request.json['usernumber']
    comment = request.json['comment']
    new_user = User(username, usernumber, comment)
    db.session.add(new_user)
    db.session.commit()
    return user_schema.jsonify(new_user)

@bp.route('/user', methods=['GET'])
def get_users():
    all_users = User.query.all()
    result = users_schema.dump(all_users)
    return jsonify(result)

@bp.route('/user/<id>', methods=['GET'])
def get_user(id):
    user = User.query.get(id)
    return user_schema.jsonify(user)

@bp.route('/user/<id>', methods=['PUT'])
def update_user(id):
    user = User.query.get(id)
    username = request.json['username']
    usernumber = request.json['usernumber']
    comment = request.json['comment']
    user.username = username
    user.usernumber = usernumber
    user.comment = comment
    db.session.commit()
    return user_schema.jsonify(user)

@bp.route('/user/<id>', methods=['DELETE'])
def delete_user(id):
    user = User.query.get(id)
    db.session.delete(user)
    db.session.commit()
    return user_schema.jsonify(user)

app.register_blueprint(bp, url_prefix='/api')

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

• POST /api/user: Create a new user.
• GET /api/user: Retrieve a list of all users.
• GET /api/user/<id>: Retrieve a single user by ID.
• PUT /api/user/<id>: Update a user by ID.
• DELETE /api/user/<id>: Delete a user by ID.

Note:

1. This is a very basic CRUD application and doesn't have any security measures. In a real-world application, you would want to add authentication, input sanitization, error handling, etc.
2. Replace 'mysql://username:password@localhost/dbname' with your MySQL database details.
3. Also, don't forget to run the DB (Xampp)
   

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