Month: June 2020

1. create_db.py

import sqlalchemy
from urllib import parse
engine = sqlalchemy.create_engine('mysql://zhuby:%s@192.168.0.43' % parse.unquote_plus('somIUpass#98'))
engine.execute("CREATE DATABASE TESTDB") #create db
engine.execute("USE TESTDB") # select new db

2. create_db2.py

import sqlalchemy
from urllib import parse
from sqlalchemy_utils import database_exists, create_database

engine = sqlalchemy.create_engine('mysql://zhuby:%s@192.168.0.43/EmployeeDB3' % parse.unquote_plus('somIUpass#98'))

if not database_exists(engine.url):
    create_database(engine.url)

print(database_exists(engine.url))

3. create_db3.py

from sqlalchemy import create_engine
user = 'zhuby'
password = 'somIUpass#98'
host = '192.168.0.43'
port = '3306'
db = 'NEWDB2'
# This engine just used to query for list of databases
mysql_engine = create_engine('mysql://{0}:{1}@{2}:{3}'.format(user, password, host, port))
# Query for existing databases
mysql_engine.execute("CREATE DATABASE IF NOT EXISTS {0} ".format(db))
# Go ahead and use this engine
db_engine = create_engine('mysql://{0}:{1}@{2}:{3}/{4}'.format(user, password, host, port, db))

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from flask_script import Manager
from flask_migrate import Migrate, MigrateCommand
from urllib import parse
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql+pymysql://zhuby:%s@192.168.0.43/EmployeeDB' % parse.unquote_plus('somIUpass#98')

db = SQLAlchemy(app)
migrate = Migrate(app, db)

manager = Manager(app)
manager.add_command('db', MigrateCommand)

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(128))

if __name__ == '__main__':
    manager.run()

Assuming the above script is stored in a file named manage.py, all the database migration commands can be accessed by running the script:

$ python manage.py db init
$ python manage.py db migrate
$ python manage.py db upgrade
$ python manage.py db --help

When DB user password contains special characters, we can make the connection string as:
from urllib import parse
from sqlalchemy.engine import create_engine
engine = create_engine(‘postgres://user:%s@host/database’ % parse.unquote_plus(‘badpass’))
Here is an example hello.py:

import os
from flask import Flask, render_template, session, redirect, url_for, flash
from flask_bootstrap import Bootstrap
from flask_moment import Moment
from flask_wtf import FlaskForm
from wtforms import StringField, SubmitField
from wtforms.validators import DataRequired
from flask_sqlalchemy import SQLAlchemy
from urllib import parse
basedir = os.path.abspath(os.path.dirname(__file__))

app = Flask(__name__)

app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql+pymysql://zhuby:%s@192.168.0.43/EmployeeDB' % parse.unquote_plus('somIUpass#98')
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False


bootstrap = Bootstrap(app)
moment = Moment(app)
db = SQLAlchemy(app)


class Role(db.Model):
    __tablename__ = 'roles'
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(64), unique=True)
    users = db.relationship('User', backref='role')

    def __repr__(self):
        return '<Role %r>' % self.name


class User(db.Model):
    __tablename__ = 'users'
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(64), unique=True, index=True)
    role_id = db.Column(db.Integer, db.ForeignKey('roles.id'))

    def __repr__(self):
        return '<User %r>' % self.username


class NameForm(FlaskForm):
    name = StringField('What is your name?', validators=[DataRequired()])
    submit = SubmitField('Submit')


@app.errorhandler(404)
def page_not_found(e):
    return render_template('404.html'), 404


@app.errorhandler(500)
def internal_server_error(e):
    return render_template('500.html'), 500


@app.route('/', methods=['GET', 'POST'])
def index():
    form = NameForm()
    if form.validate_on_submit():
        old_name = session.get('name')
        if old_name is not None and old_name != form.name.data:
            flash('Looks like you have changed your name!')
        session['name'] = form.name.data
        return redirect(url_for('index'))
    return render_template('index.html', form=form, name=session.get('name'))

verify the code with python commands:
(venv) C:\Users\zhuby\flasky>python
Python 3.8.3 (tags/v3.8.3:6f8c832, May 13 2020, 22:37:02) [MSC v.1924 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> from hello import db
>>> db.create_all()
C:\Users\zhuby\python\flask_db_api\venv\lib\site-packages\pymysql\cursors.py:170: Warning: (3719, "'utf8' is currently an alias for the character set UTF8MB3, but will be an alias for UTF8MB4 in a future release. Please consider using UTF8MB4 in order to be unambiguous.")
  result = self._query(query)
>>> from hello import Role, User
>>> admin_role = Role(name='Admin')
>>> mod_role = Role(name='Moderator')
>>> user_role = Role(name='User')
>>> user_john = User(username='john', role=admin_role)
>>> user_susan = User(username='susan', role=user_role)
>>> db.session.add(admin_role)
>>> db.session.add(mod_role)
>>> db.session.add(user_role)
>>> db.session.add(user_john)
>>> db.session.add(user_susan)
>>> db.session.commit()
>>> print(admin_role.id)
1
>>> print(user_role.id)
3
>>> Role.query.all()
[<Role 'Admin'>, <Role 'Moderator'>, <Role 'User'>]
>>> User.query.all()
[<User 'john'>, <User 'susan'>]
>>> User.query.filter_by(role=user_role).all()
[<User 'susan'>]