How to Generate Flask-SQLAlchemy Models Using Vertabelo

Flask is a web microframework for Python. It uses Flask-SQLAlchemy for object relational mapping. It is a Flask wrapper for SQLAlchemy – a powerful relational database framework that offers a high level ORM and low level access to a database’s native SQL functionality.

For each database table, SQLAlchemy uses a regular Python class with attributes that match the columns of a corresponding database table. The database instance from Flask-SQLAlchemy provides a base class for models called db.Model.

Now, you can generate Flask-SQLAlchemy classes using the online database modeler Vertabelo and a Python script called vertabelo-flask, which is hosted on GitHub.

Installation

Clone the repo:

git clone https://github.com/Vertabelo/vertabelo-flask.git

Usage

• First, log in to your Vertabelo account and create a new database model or import an existing database structure using a reverse engineering tool. If you don’t have an account, you can register for a trial plan here.

  Note that in Vertabelo you can also import a database structure from SQL script.

  Assume that we have our model created and opened in Vertabelo. For our purposes we will use the following example:

  
  
  
  
  

• Download the model as an XML file.

  

  
  

• Generate classes using the script:

  ./vertabelo_flask_sqlalchemy.py -i employees.xml -o model.py

  
  

• The output file contains Python classes.

  # -*- encoding: utf-8 -*-
  # begin
  
  from flask.ext.sqlalchemy import SQLAlchemy
  
  app = Flask(__name__)
  db = SQLAlchemy(app)
  
  
  
  class Employee (db.Model):
      __tablename__ = "employee"
      id = db.Column('id', db.Integer, primary_key=True)
      name = db.Column('name', db.Unicode)
      surname = db.Column('surname', db.Unicode)
      address = db.Column('address', db.Unicode)
      phone_number = db.Column('phone_number', db.Unicode)
  
  
  class Schedule (db.Model):
      __tablename__ = "schedule"
      id = db.Column('id', db.Integer, primary_key=True)
      employee_id = db.Column('employee_id', db.Integer, db.ForeignKey('employee.id'))
      work_date = db.Column('work_date', db.Date)
      start_work_hour = db.Column('start_work_hour', db.BigInteger)
      end_work_hour = db.Column('end_work_hour', db.BigInteger)
      is_holiday = db.Column('is_holiday', db.Boolean)
      is_weekend = db.Column('is_weekend', db.Boolean)
  
      employee = db.relationship('Employee', foreign_keys=employee_id)
  
  
  # end
  

It’s possible to use SQLAlchemy in Flask directly. To generate SQLAlchemy classes, follow the instructions: Visual design of SQLAlchemy models in 6 steps.