I am new to Flask and currently exploring the official tutorial available in https://flask.palletsprojects.com/en/2.0.x/tutorial/factory/.

The example creates a blog based on a SQLite database. The database is defined in the following statement:

app.config.from_mapping(
        SECRET_KEY='dev',
        DATABASE=os.path.join(app.instance_path, 'flaskr.sqlite'),
    )

Program Code

flaskr/__init__.py
import os

from flask import Flask


def create_app(test_config=None):
    # create and configure the app
    app = Flask(__name__, instance_relative_config=True)
    app.config.from_mapping(
        SECRET_KEY='dev',
        DATABASE=os.path.join(app.instance_path, 'flaskr.sqlite'),
    )

    if test_config is None:
        # load the instance config, if it exists, when not testing
        app.config.from_pyfile('config.py', silent=True)
    else:
        # load the test config if passed in
        app.config.from_mapping(test_config)

    # ensure the instance folder exists
    try:
        os.makedirs(app.instance_path)
    except OSError:
        pass

    # a simple page that says hello
    @app.route('/hello')
    def hello():
        return 'Hello, World!'

    return app

However, instead of am SQLite database, I want to use a MySQL database for storing information. How can I define the MySQL configuration at this stage?

I have modified the following code in the db.py file of the tutorial:

https://flask.palletsprojects.com/en/2.0.x/tutorial/database/

import mysql.connector
import click
from flask import current_app, g
from flask.cli import with_appcontext

# Function to create a database connection.
def get_db():
    if 'db' not in g:
        g.db=mysql.connector.connect(host="localhost",user="dbuser",password="database123",database="testdb")
    return g.db

# Function to close an existing database connection.
def close_db(e=None):
    db=g.pop('db',None)
    if db is not None:
        db.close()

# Function to initialize the database from a script.
def init_db():
    db = get_db()
    with open('schema.sql', 'r') as f:
        with db.cursor() as cursor:
            cursor.execute(f.read(), multi=True)
        db.commit()

@click.command('init-db')
@with_appcontext
def init_db_command():
    # Delete existing data and re-create tables.
    init_db()
    click.echo('Initialized the database.')

# Register with the application.
def init_app(app):
    app.teardown_appcontext(close_db)
    app.cli.add_command(init_db_command)

Can someone please provide some guidance on how to setup a MySQL database connection?

CodePudding user response：

Here you can use pymysql to manage your connections. Below is an example showing that how you can manage the DB connection.

import pymysql


def db_connect():
    conn = pymysql.connect(user='Your user',
                           password="Your password",
                           host="Your host",
                           database="Your database",
                           cursorclass=pymysql.cursors.DictCursor)
    return conn


def db_close(conn):
    if conn and conn.open:
        conn.close()


class DatabaseHandler(object):
    def __init__(self):
        self.conn = None

    def __enter__(self):
        self.conn = db_connect()
        return self.conn

    def __exit__(self, exc_type, exc_val, exc_tb):
        db_close(self.conn) 

You can use it as,

with DatabaseHandler() as db_conn:
     Any database operation with db_conn

CodePudding user response：

I did some digging around and figured that it is not mandatory to define the MySQL database connection inside the factory function for the application to work. I removed the database parameter values from app.config.from_mapping and only kept the database connection string inside the actual db.py file. So far, the application has been working fine.

app=Flask(__name__, instance_relative_config=True)
    app.config.from_mapping(SECRET_KEY='development',)