Front Matter — Alembic 1.15.2 documentation

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# Front Matter

Information about the Alembic project.

## Project Homepage

Alembic is hosted on GitHub at sqlalchemy/alembic under the SQLAlchemy organization.

Releases and project status are available on Pypi at https://pypi.python.org/pypi/alembic.

The most recent published version of this documentation should be at https://alembic.sqlalchemy.org.

## Installation

While Alembic can be installed system wide, it’s more common that it’s installed local to a virtual environment , as it also uses libraries such as SQLAlchemy and database drivers that are more appropriate for local installations.

The documentation below is only one kind of approach to installing Alembic for a project; there are many such approaches. The documentation below is provided only for those users who otherwise have no specific project setup chosen.

To build a virtual environment for a specific project, first we assume that Python virtualenv is installed systemwide. Then:

    $ cd /path/to/your/project
    $ virtualenv .venv

There is now a Python interpreter that you can access in `/path/to/your/project/.venv/bin/python`, as well as the pip installer tool in `/path/to/your/project/.venv/bin/pip`.

We now install Alembic as follows:

    $ /path/to/your/project/.venv/bin/pip install alembic

The install will add the `alembic` command to the virtual environment. All operations with Alembic in terms of this specific virtual environment will then proceed through the usage of this command, as in:

    $ /path/to/your/project/.venv/bin/alembic init alembic

The next step is optional. If our project itself has a `setup.py` file, we can also install it in the local virtual environment in editable mode:

    $ /path/to/your/project/.venv/bin/pip install -e .

If we don’t “install” the project locally, that’s fine as well; the default `alembic.ini` file includes a directive `prepend_sys_path = .` so that the local path is also in `sys.path`. This allows us to run the `alembic` command line tool from this directory without our project being “installed” in that environment.

As a final step, the virtualenv activate tool can be used so that the `alembic` command is available without any path information, within the context of the current shell:

    $ source /path/to/your/project/.venv/bin/activate

### Dependencies

Alembic’s install process will ensure that SQLAlchemy is installed, in addition to other dependencies. Alembic will work with SQLAlchemy as of version 1.4.0.

Changed in version 1.15.0: Support for SQLAlchemy older than 1.4.0 was dropped.

Alembic supports Python versions 3.9 and above

Changed in version 1.15: Alembic now supports Python 3.9 and newer.

### Versioning Scheme

Alembic’s versioning scheme is based on that of SQLAlchemy’s versioning scheme. In particular, it should be noted that while Alembic uses a three-number versioning scheme, it does not use SemVer. In SQLAlchemy and Alembic’s scheme, the middle digit is considered to be a “Significant Minor Release”, which may include removal of previously deprecated APIs with some risk of non-backwards compatibility in a very small number of cases.

This means that version “1.8.0”, “1.9.0”, “1.10.0”, “1.11.0”, etc. are Significant Minor Releases, which will include new API features and may remove or modify existing ones.

Therefore, when pinning Alembic releases, pin to the “major” and “minor” digits to avoid API changes.

A true “Major” release such as a change to “2.0” would include complete redesigns/re-architectures of foundational features; currently no such series of changes are planned, although changes such as replacing the entire “autogenerate” scheme with a new approach would qualify for that level of change.

## Community

Alembic is developed by Mike Bayer, and is part of the SQLAlchemy project.

User issues, discussion of potential bugs and features are most easily discussed using GitHub Discussions.

## Bugs

Bugs and feature enhancements to Alembic should be reported on the GitHub issue tracker.