Current File : //opt/alt/python37/share/doc/alt-python37-alembic/docs/build/api/commands.rst
.. _alembic.command.toplevel:
=========
Commands
=========
.. note:: this section discusses the **internal API of Alembic**
as regards its command invocation system.
This section is only useful for developers who wish to extend the
capabilities of Alembic. For documentation on using Alembic commands,
please see :doc:`/tutorial`.
Alembic commands are all represented by functions in the :ref:`alembic.command.toplevel`
package. They all accept the same style of usage, being sent
the :class:`.Config` object as the first argument.
Commands can be run programmatically, by first constructing a :class:`.Config`
object, as in::
from alembic.config import Config
from alembic import command
alembic_cfg = Config("/path/to/yourapp/alembic.ini")
command.upgrade(alembic_cfg, "head")
In many cases, and perhaps more often than not, an application will wish
to call upon a series of Alembic commands and/or other features. It is
usually a good idea to link multiple commands along a single connection
and transaction, if feasible. This can be achieved using the
:attr:`.Config.attributes` dictionary in order to share a connection::
with engine.begin() as connection:
alembic_cfg.attributes['connection'] = connection
command.upgrade(alembic_cfg, "head")
This recipe requires that ``env.py`` consumes this connection argument;
see the example in :ref:`connection_sharing` for details.
To write small API functions that make direct use of database and script directory
information, rather than just running one of the built-in commands,
use the :class:`.ScriptDirectory` and :class:`.MigrationContext`
classes directly.
.. automodule:: alembic.command
:members:
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