API Reference

class flask_alembic.Alembic(app=None, run_mkdir=True, command_name='db')

Provide an Alembic environment and migration API.

If instantiated without an app instance, init_app() is used to register an app at a later time.

Configures basic logging to stderr for the sqlalchemy and alembic loggers if they do not already have handlers.

Parameters:

  • app – Call init_app on this app.

  • run_mkdir – Run mkdir() during init_app.

  • command_name – Register a Click command with this name during init_app, or skip if False.

init_app(app, run_mkdir=None, command_name=None)

Register this extension on an app. Will automatically set up migration directory by default.

Keyword arguments on this method override those set during __init__() if not None.

Parameters:

  • app – App to register.

  • run_mkdir – Run mkdir() automatically.

  • command_name – Register a Click command with this name, or skip if False.

rev_id()

Generate a unique id for a revision.

By default this uses alembic.util.rev_id(). Override this method, or assign a static method, to change this.

For example, to use the current timestamp:

alembic = Alembic(app)
alembic.rev_id = lambda: str(datetime.utcnow().timestamp())
property config

Get the Alembic Config for the current app.

property script_directory

Get the Alembic ScriptDirectory for the current app.

property environment_context

Get the Alembic EnvironmentContext for the current app.

property migration_context

Get the Alembic MigrationContext for the current app.

Accessing this property opens a database connection but can’t close it automatically. Make sure to call migration_context.connection.close() when you’re done.

property op

Get the Alembic Operations context for the current app.

Accessing this property opens a database connection but can’t close it automatically. Make sure to call migration_context.connection.close() when you’re done.

run_migrations(fn, **kwargs)

Configure an Alembic MigrationContext to run migrations for the given function.

This takes the place of Alembic’s env.py file, specifically the run_migrations_online function.

Parameters:

  • fn – Use this function to control what migrations are run.

  • kwargs – Extra arguments passed to upgrade or downgrade in each revision.

mkdir()

Create the script directory and template.

current()

Get the list of current revisions.

heads(resolve_dependencies=False)

Get the list of revisions that have no child revisions.

Parameters:

resolve_dependencies – Treat dependencies as down revisions.

branches()

Get the list of revisions that have more than one next revision.

log(start='base', end='heads')

Get the list of revisions in the order they will run.

Parameters:

  • start – Only get entries since this revision.

  • end – Only get entries until this revision.

stamp(target='heads')

Set the current database revision without running migrations.

Parameters:

target – Revision to set to.

upgrade(target='heads')

Run migrations to upgrade database.

Parameters:

target – Revision to go up to.

downgrade(target=-1)

Run migrations to downgrade database.

Parameters:

target – Revision to go down to.

revision(message, empty=False, branch='default', parent='head', splice=False, depend=None, label=None, path=None)

Create a new revision. By default, auto-generate operations by comparing models and database.

Parameters:

  • message – Description of revision.

  • empty – Don’t auto-generate operations.

  • branch – Use this independent branch name.

  • parent – Parent revision(s) of this revision.

  • splice – Allow non-head parent revision.

  • depend – Revision(s) this revision depends on.

  • label – Label(s) to apply to this revision.

  • path – Where to store this revision.

Returns:

List of new revisions.

merge(revisions='heads', message=None, label=None)

Create a merge revision.

Parameters:

  • revisions – Revisions to merge.

  • message – Description of merge, will default to revisions param.

  • label – Label(s) to apply to this revision.

Returns:

A new revision object.

produce_migrations()

Generate the MigrationScript object that would generate a new revision.

compare_metadata()

Generate a list of operations that would be present in a new revision.