Flask SQL Alchemy is a library that is intended to make it easy to do something against a database, such as creating a database, creating tables, inserting data, and so on. Instead of having to write complex SQL commands, simple SQL Alchemy directives are used.

Use the pip install command to install the Flask SQL Alchemy and mySQL packages.

pip install flask-sqlalchemy
pip install mysql
pip install mysql-connector-python

Or, you can specify the version to install

pip install flask-sqlalchemy==3.0.2
pip install mysql==0.0.3
pip install mysql-connector-python==8.1.0

Or, better yet, use a requirements.txt file.

Flask-SQLAlchemy==3.0.5
mysql==0.0.3
mysql-connector-python==8.1.0

And then install the packages using the requirements.txt file.

pip install --requirement requirements.txt

You will need to know the username and password of your mySQL user that is allowed to make a remote connection. If you are able to log into your mySQL server, the select * from mysql.user can be used to list your users. Something like this should be returned for each user. In this example, user john.doe is allowed to make a connection to Host % (remote).

You will also want to ensure mySQL is configured to allow remote connections. Check out my article Configure mySQL or MariaDB to allow remote connections on Docker.

                  Host: %
                  User: john.doe
              Password: *B87A204DF7CFB2D1ABC123456JFH0DC081CD35EF2
           Select_priv: Y
           Insert_priv: Y
           Update_priv: Y
           Delete_priv: Y
           Create_priv: Y
             Drop_priv: Y
           Reload_priv: N
         Shutdown_priv: N
          Process_priv: N
             File_priv: N
            Grant_priv: Y
       References_priv: N
            Index_priv: N
            Alter_priv: Y
          Show_db_priv: N
            Super_priv: N
 Create_tmp_table_priv: N
      Lock_tables_priv: N
          Execute_priv: N
       Repl_slave_priv: N
      Repl_client_priv: N
      Create_view_priv: N
        Show_view_priv: N
   Create_routine_priv: N
    Alter_routine_priv: N
      Create_user_priv: N
            Event_priv: N
          Trigger_priv: N
Create_tablespace_priv: N
              ssl_type:
            ssl_cipher:
           x509_issuer:
          x509_subject:
         max_questions: 0
           max_updates: 0
       max_connections: 0
  max_user_connections: 0
                plugin:
 authentication_string:

create_engine(uri) is used to make the initial connection to mySQL. In this example, create_engine(uri) is in __init__.py.

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from sqlalchemy import create_engine, func, exc

db = SQLAlchemy()

def app_obj():
    app = Flask(__name__)
    uri = "mysql://john.doe:itsasecret@mysql.example.com/mydatabase"
    app.config['SQLALCHEMY_DATABASE_URI'] = uri
    app.config["SQLALCHEMY_TRACK_MODIFICATIONS"] = False
    db.init_app(app)

    with app.app_context():
        db.create_engine(uri)

    return app

And then your view, such as views.py, engine.connect() can be used to test the connection to mySQL.

from flask import Blueprint
from . import app, db
from sqlalchemy import exc

views = Blueprint('views', __name__)

@views.route('/')
def home():
    try:
        db.engine.connect()
    except exc.SQLAlchemyError as sqlalchemyerror:
        return sqlalchemyerror
    except Exception as exception:
        return exception
    else:
        return "no exceptions were raised - it appears the connection to mySQL was successful"