flask_migrate.md

Flask Stuff

Notes from 6/28

Today's tasks:

• Use flask-migrate to manage db state
• manage flash messages with session
• hash + salt with flask bcrypt

Setup instructions

• mkvirtualenv flask_migrate
• structure: root
  • templates
    • base.html
    • index.html
    • new.html
  • app.py
• pip install flask flask_sqlalchemy psycopg2 flask_migrate
• pip freeze > requirements.txt
• createdb learn-flask-migrate

Making the application

from flask import Flask
from flask_sqlalchemy import SQLAlchemy



app = Flask(__name__)
db = SQLAlchemy(app)

app.config['SQLALCHEMY_DATABASE_URI'] = 'postgres://localhost/learn-flask-migrate'


if __name__ == '__main__':
  app.run(debug=True, port=3000)

Make a model next. At this point, the password is still insecure, but we will refactor later.

class User(db.Model):
  id = db.Column(db.Integer, primary_key=True)
  username = db.Column(db.Text, nullable=False)
  password = db.Column(db.Text, nullable=False)

  def __init__(self, username, password):
    self.username = username
    self.password = password

Create a new file, manage.py
In manage.py, insert the following:

from app import app, db

from flask_script import Manager # this class handles command line script initialization

from flask_migrate import Migrate, MigrateCommand
# Migrate - handles migration initialization
# MigrateCommand - specifies what command line task runs our migrations

# Initialize flask_migrate
  # Need to specify the application and db you are using
migrate = Migrate(app, db)

# Initialize flask_script
manager = Manager(app)


# Specify what string gets attached to the MigrateCommand
manager.add_command('db', MigrateCommand)




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

Now, python manage.py db in the terminal will bring up a list arguments available to flask_migrate

Steps

1 Run python manage.py db init to create a migrations folder with alembic setup files 2 python manage.py db migrate 3 python manage.py db upgrade

You can then upgrade or downgrade as necessary.

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## Notes + flask_migrate is an extension of something called "alembic" + flask_script allows you to run shell scripts out of flask