get_x_argument

get_x_argument(as_dictionary: Literal[False] = False) → List[str]

get_x_argument(as_dictionary: Literal[True] = False) → Dict[str, str]

Return the value(s) passed for the -x argument, if any.

The -x argument is an open ended flag that allows any user-defined value or values to be passed on the command line, then available here for consumption by a custom env.py script.

The return value is a list, returned directly from the argparse structure. If as_dictionary=True is passed, the x arguments are parsed using key=value format into a dictionary that is then returned.

For example, to support passing a database URL on the command line, the standard env.py script can be modified like this:

cmd_line_url = context.get_x_argument(
    as_dictionary=True).get('dbname')
if cmd_line_url:
    engine = create_engine(cmd_line_url)
else:
    engine = engine_from_config(
            config.get_section(config.config_ini_section),
            prefix='sqlalchemy.',
            poolclass=pool.NullPool)

This then takes effect by running the alembic script as:

alembic -x dbname=postgresql://user:pass@host/dbname upgrade head

This function does not require that the MigrationContext has been configured.

See also:

• EnvironmentContext.get_tag_argument()
• Config.cmd_opts