Classe « Session »

Méthode sqlalchemy.orm.Session.begin

Signature de la méthode begin

def begin(self, subtransactions=False, nested=False, _subtrans=False) 

Description

begin.__doc__

Begin a transaction, or nested transaction,
        on this :class:`.Session`, if one is not already begun.

        The :class:`_orm.Session` object features **autobegin** behavior,
        so that normally it is not necessary to call the
        :meth:`_orm.Session.begin`
        method explicitly. However, it may be used in order to control
        the scope of when the transactional state is begun.

        When used to begin the outermost transaction, an error is raised
        if this :class:`.Session` is already inside of a transaction.

        :param nested: if True, begins a SAVEPOINT transaction and is
         equivalent to calling :meth:`~.Session.begin_nested`. For
         documentation on SAVEPOINT transactions, please see
         :ref:`session_begin_nested`.

        :param subtransactions: if True, indicates that this
         :meth:`~.Session.begin` can create a "subtransaction".

         .. deprecated:: 1.4 The :paramref:`_orm.Session.begin.subtransactions` flag is deprecated and will be removed in SQLAlchemy version 2.0.  See the documentation at :ref:`session_subtransactions` for background on a compatible alternative pattern.



        :return: the :class:`.SessionTransaction` object.  Note that
         :class:`.SessionTransaction`
         acts as a Python context manager, allowing :meth:`.Session.begin`
         to be used in a "with" block.  See :ref:`session_autocommit` for
         an example.

        .. seealso::

            :ref:`session_autobegin`

            :ref:`unitofwork_transaction`

            :meth:`.Session.begin_nested`