CODEWITHSUNDEEP
pythonflasksqlalchemyflask-sqlalchemy
Leyo R
Leyo R

Reputation: 723

How to create classes from existing tables using Flask-SQLaclhemy

I know I need to use the MetaData object, in SQLAlchemy, but I am not sure how to use it with a class,

db = SQLAlchemy(app)
meta =db.Metadata()
class orders(db.model):
  pass

How do I pass the meta object to the class so that it will auto generate table schema?

Upvotes: 7

Views: 10103

Answers (3)

Matt
Matt

Reputation: 530

The db.Model.metadata.reflect(...) function is also super useful here; you don't have to define the model at all (it's just inferred from the existing database schema).

See stay_hungry's answer here for a specific implementation

Upvotes: 0

VERNSTOKED
VERNSTOKED

Reputation: 117

You can use sqlacodegen to generate the classes needed for sqlalchemy. 

pip install sqlacodegen

sqlacodegen postgresql+psycopg2://username:password@host/database --outfile models.py

I ran into an issue with the Base class and the query attribute. The error I received was:

AttributeError: type object 'PaymentType' has no attribute 'query'

I was able to make the sqlacodegen classes work by using a scoped_session.

session = scoped_session(sessionmaker(autocommit=False,autoflush=False,bind=engine))
Base.query = session.query_property()
print(PaymentType.query.all())

Upvotes: 4

Codejunky
Codejunky

Reputation: 632

Well you can use SQLAlchemy's autoload feature but I still haven't figured out how to use that from flask-sqlalchemy. Here's a tutorial if you want to read about it anyway: SQLAlchemy Connecting to pre-existing databases. The best solution I found for the time being is to use sqlautocode to generate the SQLAlchemy models from the existing tables in your database. I know it would be preferable if SQLAlchemy would handle that automatically but I can't find a way to do it from Flask.

Here's how to use it:

sqlautocode mysql://<dbuser>:<pass>@localhost:3306/<dbname> -o alchemy_models.py

This will generate the Models and place them in the alchemy_models.py file. I hope this helps

Upvotes: 7

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