Can you explain how Alembic works for managing database migrations?

Alembic is a tool for managing database migrations in Python projects, typically used with SQLAlchemy. It allows tracking changes in the database schema and applying them sequentially.

Main mechanisms of Alembic:

1. Migration scripts — Alembic stores migrations as Python scripts that describe schema changes (creating tables, modifying columns, etc.).

2. Versioning — each migration has a unique identifier (revision), and Alembic keeps the current database version in a special table.

3. Automatic migration generation — Alembic can compare the current data model (e.g., SQLAlchemy models) with the database state and generate migration scripts.

4. Applying and rolling back migrations — using the commands alembic upgrade and alembic downgrade, you can apply or revert migrations to the desired version.

Example command to create a migration:

alembic revision --autogenerate -m "Add users table"

Example of applying migrations:

alembic upgrade head

Thus, Alembic helps manage database changes in a sequential and safe manner, especially in team development.