Using SQLAlchemy models in and out of Flask

by

flask_sqlalchemy doesn`t allow you to use it outside of a Flask context. However, you can create models via SQLAlchemy itself. So your database.py file would look like this:

from sqlalchemy import MetaData, Column, Integer, String
from sqlalchemy.ext.declarative import declarative_base

metadata = MetaData()
Base = declarative_base(metadata=metadata)

class Job(Base):
    __tablename__ = 'job'
    
    job_id = Column(Integer, primary_key=True)
    description = Column(String(256))
    
    def __init__(self, description):
        self.description = description

You can initialize a flask_sqlalchemy object using produced metadata (flaskdb.py):

from flask_sqlalchemy import SQLAlchemy

from database import metadata

db = SQLAlchemy(metadata=metadata)

And you initialize your Flask app like this:

from flask import Flask

from flaskdb import db

def create_app(config):
    app = Flask('web_service')
    app.config.from_object(config)
    
    db.init_app(app)

Created models can be used outside of the Flask context via a Session. For example:

from sqlalchemy import create_engine
from sqlalchemy.orm import Session

from database import metadata, Job

engine = create_engine('your://database@configuration/here')
session = Session(engine)
jobs = session.query(Job).all()
session.close()

As a downside of this approach, you can’t use direct access to database objects through models. Instead, you are forced to use Sessions:

from database import Job
from flaskdb import db

Job.query.all() # Does not work
db.session.query(Job).all() # Works

More Related Contents:

  1. How to execute raw SQL in Flask-SQLAlchemy app
  2. jsonify a SQLAlchemy result set in Flask [duplicate]
  3. Flask SQLAlchemy query, specify column names
  4. SQLAlchemy ORM conversion to pandas DataFrame
  5. AttributeError: can’t set attribute when connecting to sqlite database with flask-sqlalchemy
  6. Case Insensitive Flask-SQLAlchemy Query
  7. How to update SQLAlchemy row entry?
  8. Flask-SQLalchemy update a row’s information
  9. How to build a flask application around an already existing database?
  10. SQLAlchemy ManyToMany secondary table with additional fields
  11. Can SQLAlchemy be used with Google Cloud SQL?
  12. Updates to JSON field don’t persist to DB
  13. Flask sqlalchemy many-to-many insert data
  14. How to delete a record by id in Flask-SQLAlchemy
  15. Get inserted key before commit session
  16. Querying with function on Flask-SQLAlchemy model gives BaseQuery object is not callable error
  17. AttributeError: ‘int’ object has no attribute ‘_sa_instance_state’
  18. sqlalchemy.exc.NoSuchModuleError: Can’t load plugin: sqlalchemy.dialects:postgres
  19. SQLAlchemy – performing a bulk upsert (if exists, update, else insert) in postgresql
  20. Getting first row from sqlalchemy
  21. ImportError: No module named sqlalchemy
  22. flask-sqlalchemy or sqlalchemy
  23. Flask-SQLAlchemy Constructor
  24. Retrieve query results as dict in SQLAlchemy
  25. SQLAlchemy ordering by count on a many to many relationship
  26. flask sqlalchemy query with keyword as variable
  27. How can I bind a list to a parameter in a custom query in SQLAlchemy?
  28. How to disable SQLAlchemy caching?
  29. sqlalchemy unique across multiple columns
  30. Multi-threaded use of SQLAlchemy

Leave a Comment