Flask-Alembic

Flask-Alembic is a Flask extension that provides a configurable Alembic migration environment around a Flask-SQLAlchemy database.

Installation

Install from PyPI:

$ pip install Flask-Alembic

Basic Usage

You've created a Flask application and some models with Flask-SQLAlchemy. Now start using Flask-Alembic:

from flask_alembic import Alembic

# Intialize the extension
alembic = Alembic()
alembic.init_app(app)

Commands are added to the flask CLI:

$ flask db --help
$ flask db revision "making changes"
$ flask db upgrade

You can also access Alembic's functionality from Python:

with app.app_context():
    # Auto-generate a migration
    alembic.revision('making changes')

    # Upgrade the database
    alembic.upgrade()

    # Access the internals
    environment_context = alembic.env

Differences from Alembic

• Configuration is taken from Flask.config instead of alembic.ini and env.py.
• The migrations are stored directly in the migrations folder instead of the versions folder.
• Provides the migration environment instead of env.py and exposes Alembic's internal API objects.
• Differentiates between CLI commands and Python functions. The functions return revision objects and don't print to stdout.
• Allows operating Alembic at any API level while the app is running, through the exposed objects and functions.
• Does not (currently) support offline migrations. I don't plan to add this but am open to patches.
• Does not (currently) support multiple databases. I plan on adding support for Flask-SQLAlchemy binds and external bases eventually, or am open to patches.
• Adds a system for managing independent migration branches and makes it easier to work with named branches.